linux: build musl with Clang

We build everything else with Clang. And musl's configure looks at the
invoking compiler to see which wrapper scripts to install. So we need
to compile with clang to get those wrapper scripts installed.

Author: indygreg

cpython-linux/build-musl.sh

@@ -7,6 +7,9 @@ set -e
 
 cd /build
 
+export PATH=/tools/${TOOLCHAIN}/bin:/tools/host/bin:$PATH
+export CC=clang
+
 tar -xf musl-${MUSL_VERSION}.tar.gz
 
 pushd musl-${MUSL_VERSION}

cpython-linux/build.py

@@ -332,11 +332,13 @@ def build_musl(client, image):
     musl_archive = download_entry('musl', BUILD)
 
     with run_container(client, image) as container:
+        copy_toolchain(container)
         copy_file_to_container(musl_archive, container, '/build')
         copy_file_to_container(SUPPORT / 'build-musl.sh', container, '/build')
 
         env = {
             'MUSL_VERSION': DOWNLOADS['musl']['version'],
+            'TOOLCHAIN': 'clang-linux64',
         }
 
         container_exec(container, '/build/build-musl.sh',