Dockerfile: bump Alpine Linux version (oetiker#624)

* Dockerfile: bump Alpine Linux version

Following https://stackoverflow.com/a/73374817/4715872 suggestions:
Alpine signing key was rotated, so new package builds are not
trusted by the old image

Signed-off-by: Jim Klimov <jimklimov@gmail.com>

* Dockerfile: install Test/SharedFork for tests

 372.3 Can't locate Test/SharedFork.pm in @inc (you may need to install the Test::SharedFork module) (@inc contains: /usr/local/src/t/../bin /usr/local/src/t/..//thirdparty/lib/perl5/5.30.3/x86_64-linux-gnu /usr/local/src/t/..//thirdparty/lib/perl5/5.30.3 /usr/local/src/t/..//thirdparty/lib/perl5/x86_64-linux-gnu /usr/local/src/t/..//thirdparty/lib/perl5 /usr/local/src/t/../lib ./thirdparty/lib/perl5/5.30.3/x86_64-linux-gnu ./thirdparty/lib/perl5/5.30.3 ./thirdparty/lib/perl5/x86_64-linux-gnu ./thirdparty/lib/perl5 /usr/local/lib/perl5/site_perl/5.30.3/x86_64-linux-gnu /usr/local/lib/perl5/site_perl/5.30.3 /usr/local/lib/perl5/vendor_perl/5.30.3/x86_64-linux-gnu /usr/local/lib/perl5/vendor_perl/5.30.3 /usr/local/lib/perl5/5.30.3/x86_64-linux-gnu /usr/local/lib/perl5/5.30.3) at ./t/znapzend-daemonize.t line 89.
372.3 BEGIN failed--compilation aborted at ./t/znapzend-daemonize.t line 89.

---------

Signed-off-by: Jim Klimov <jimklimov@gmail.com>

Dockerfile

@@ -1,7 +1,7 @@
 
 ##### Builder image
 ARG PERL_BUILD_VERSION=5.30-buster
-ARG ALPINE_VERSION=3.11
+ARG ALPINE_VERSION=3.19
 FROM docker.io/library/perl:${PERL_BUILD_VERSION} as builder
 
 WORKDIR /usr/local/src
@@ -41,7 +41,8 @@ CMD [ "znapzend --logto=/dev/stdout" ]
 FROM builder as test
 
 RUN \
-  cpan Devel::Cover
+  cpan Devel::Cover && \
+  cpan Test::SharedFork
 
 RUN \
   ./test.sh