multi-arch-pipeline: hack in ttyS0 for aarch64 aws image

This is a workaround to get console=ttyS0,115200n8 into the
aarch64 AWS image. It does so by applying the following patch
to gf-platformid:

```diff
diff --git a/usr/lib/coreos-assembler/gf-platformid b/usr/lib/coreos-assembler/gf-platformid
index 2912b322c..36d089651 100755
--- a/usr/lib/coreos-assembler/gf-platformid
+++ b/usr/lib/coreos-assembler/gf-platformid
@@ -46,7 +46,11 @@ blscfg_path=$(coreos_gf glob-expand /boot/loader/entries/ostree-*.conf)
 coreos_gf download "${blscfg_path}" "${tmpd}"/bls.conf
 # Remove any platformid currently there
 sed -i -e 's, ignition.platform.id=[a-zA-Z0-9]*,,g' "${tmpd}"/bls.conf
-sed -i -e 's,^\(options .*\),\1 ignition.platform.id='"${platformid}"',' "${tmpd}"/bls.conf
+if [ "${platformid}" == 'aws' ]; then
+    sed -i -e 's|^\(options .*\)|\1 ignition.platform.id='"${platformid}"' console=ttyS0,115200n8|' "${tmpd}"/bls.conf
+else
+    sed -i -e 's,^\(options .*\),\1 ignition.platform.id='"${platformid}"',' "${tmpd}"/bls.conf
+fi
 coreos_gf upload "${tmpd}"/bls.conf "${blscfg_path}"

 if [ "$basearch" = "s390x" ] ; then
```

Once coreos/fedora-coreos-config#1181 and
coreos/coreos-assembler#2400 land then we
won't need this any longer.

This implements a fix for coreos/fedora-coreos-tracker#920

jobs/multi-arch-pipeline.Jenkinsfile

@@ -310,8 +310,9 @@ stages:
     - cosa buildextend-live
     - kola testiso -S --output-dir tmp/kola-metal
     - kola testiso -SP --qemu-native-4k --scenarios iso-install --output-dir tmp/kola-metal4k
-    - cosa buildextend-aws
     - cosa buildextend-openstack
+    - echo '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' | base64 --decode | sudo patch /usr/lib/coreos-assembler/gf-platformid
+    - cosa buildextend-aws
   post_commands:
     - cosa compress --compressor xz
     - tar --xz -cf tmp/kola.tar.xz tmp/kola{-basic,,-metal,-metal4k} || true