feat: add musl libc and its tools to build image (#814)

Author: danez

Dockerfile

@@ -147,6 +147,10 @@ RUN export DEBIAN_FRONTEND=noninteractive && \
         libvips-tools \
         libyaml-dev \
         mercurial \
+        # musl and musl-tools are needed for certain rust dependencies (ring) to compile correctly
+        # see https://github.com/netlify/pillar-runtime/issues/401
+        musl \
+        musl-tools \
         nasm \
         openjdk-8-jdk \
         optipng \

focal.yaml

@@ -150,3 +150,9 @@ commandTests:
     args: ["--version"]
     expectedOutput:
       - rustup 1\.\d+\.\d+
+
+  - name: "Musl library and its tools are available"
+    command: "musl-gcc"
+    args: ["--version"]
+    expectedOutput:
+      - Ubuntu 9\.4\.\d+ # version of gcc, as musl-gcc is just a wrapper