Makefile: Update base and build images

[justaugustus]

• base: debian-base:v2.0.0 --> debian-base:buster-v1.4.0
• build: golang:1.14-alpine --> golang:1.15-alpine

Signed-off-by: Stephen Augustus foo@auggie.dev

Should get cherry-picked to release-3.x.
ref: #335, https://github.com/kubernetes/release/blob/19f5fed77e43b1ec45e4fc63cbb095064a05bd6f/dependencies.yaml#L154

Partial background on debian-base image tag names: kubernetes/release#1496

$ time make container REGISTRY=fake-registry VERSION=test-tag-0
making bin/linux_amd64/git-sync
[+] Building 30.5s (15/15) FINISHED                                                                                                                                                                                               
 => [internal] booting buildkit                                                                                                                                                                                              0.8s
 => => starting container buildx_buildkit_k-release-multiarch0                                                                                                                                                               0.8s
 => [internal] load .dockerignore                                                                                                                                                                                            0.0s
 => => transferring context: 2B                                                                                                                                                                                              0.0s
 => [internal] load build definition from .dockerfile-linux_amd64                                                                                                                                                            0.0s
 => => transferring dockerfile: 3.45kB                                                                                                                                                                                       0.0s
 => [internal] load metadata for k8s.gcr.io/build-image/debian-base:buster-v1.4.0                                                                                                                                            1.4s
 => [1/8] FROM k8s.gcr.io/build-image/debian-base:buster-v1.4.0@sha256:36652ef8e4dd6715de02e9b68e5c122ed8ee06c75f83f5c574b97301e794c3fb                                                                                      2.0s
 => => resolve k8s.gcr.io/build-image/debian-base:buster-v1.4.0@sha256:36652ef8e4dd6715de02e9b68e5c122ed8ee06c75f83f5c574b97301e794c3fb                                                                                      0.0s
 => => sha256:afff10fcd513483e492807f8d934bdf0be4a237997f55e0f1f8e34c04a6cb213 528B / 528B                                                                                                                                   0.0s
 => => sha256:1813d21adc01d6699dcebdaf72ab66d2839755b536cedba34251fb39a9e9f02b 21.09MB / 21.09MB                                                                                                                             1.1s
 => => sha256:7382500cde0e9e1de04835595a1ebe2335323d8444c1a7100957c12c6d8b844f 617B / 617B                                                                                                                                   0.0s
 => => sha256:36652ef8e4dd6715de02e9b68e5c122ed8ee06c75f83f5c574b97301e794c3fb 1.69kB / 1.69kB                                                                                                                               0.0s
 => => unpacking k8s.gcr.io/build-image/debian-base:buster-v1.4.0@sha256:36652ef8e4dd6715de02e9b68e5c122ed8ee06c75f83f5c574b97301e794c3fb                                                                                    0.7s
 => [internal] load build context                                                                                                                                                                                            0.3s
 => => transferring context: 12.97MB                                                                                                                                                                                         0.2s
 => [2/8] RUN apt-get update     && apt-get -y upgrade     && apt-get -y install         ca-certificates         coreutils         socat         git         openssh-client     && rm -rf /var/lib/apt/lists/*              18.3s
 => [3/8] RUN echo "git-sync:x:65533:65533::/tmp:/sbin/nologin" >> /etc/passwd                                                                                                                                               0.3s 
 => [4/8] RUN chmod 0666 /etc/passwd                                                                                                                                                                                         0.1s 
 => [5/8] RUN echo "git-sync:x:65533:git-sync" >> /etc/group                                                                                                                                                                 0.1s 
 => [6/8] RUN mkdir -m 02775 /git && chown 65533:65533 /git                                                                                                                                                                  0.2s 
 => [7/8] WORKDIR /tmp                                                                                                                                                                                                       0.0s 
 => [8/8] ADD bin/linux_amd64/git-sync /git-sync                                                                                                                                                                             0.3s 
 => exporting to oci image format                                                                                                                                                                                            5.1s
 => => exporting layers                                                                                                                                                                                                      4.8s
 => => exporting manifest sha256:2af439389b9a8b12b15b9f121dd67cb197f1d72478c3b37a1843f0b253ca81b3                                                                                                                            0.0s
 => => exporting config sha256:650870fe217ef83e4a1761acfb944e2e93eaf5be586f3e011b55eb2df00f6cfc                                                                                                                              0.0s
 => => sending tarball                                                                                                                                                                                                       0.3s
 => importing to docker                                                                                                                                                                                                      1.5s
container: fake-registry/git-sync:test-tag-0__linux_amd64

real	0m38.543s
user	0m1.190s
sys	0m0.400s

/assign @thockin

[thockin]

Thanks. I'm happy to take this, but as discussed on slack it doesn't actually matter WRT reported vuln counts.

[thockin]

Thanks!

/lgtm
/approve

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