remove some unused packages; merge layers

Dockerfile

@@ -26,6 +26,7 @@ RUN apk add --no-cache \
     && chmod 700 "$GNUPGHOME"
 VOLUME $GNUPGHOME
 ARG PERL_MAIL_GNUPG_VERSION=0.23
+# Scalar-List-Utils-1.54 > libc-dev (sys/types.h) 
 ARG PERL_MAIL_GNUPG_BUILD_PKGS="\
     gcc \
     libc-dev \
@@ -47,13 +48,8 @@ RUN apk add --no-cache \
         perl-strictures \
         perl-sub-quote \
         perl-sub-uplevel \
-        perl-test-exception \
-        perl-test-fatal \
-        perl-test-output \
-        perl-test-requires \
         perl-try-tiny \
-        perl-type-tiny
-RUN echo TODO merge \
+        perl-type-tiny \
     && (cpanm --notest Mail::GnuPG@$PERL_MAIL_GNUPG_VERSION \
         || (cat /root/.cpanm/work/*/build.log; exit 1)) \
     && apk del $PERL_MAIL_GNUPG_BUILD_PKGS