vergen library seems to depend not only on the .git folder content but also on the git binary (#11651)

for generating COMMIT DATE and SHA reference used by the openethereum binary to display in the log. This commit
tries to solve it in the alpine docker image

Co-authored-by: Denis Granha <denis@gnosis.io>

scripts/docker/alpine/Dockerfile

@@ -11,6 +11,7 @@ RUN apk add --no-cache \
   linux-headers \
   perl \
   rust \
+  git \
   clang-dev \
   llvm-dev