Bug 1682660 - Set CMAKE_RANLIB when building compiler-rt. r=dmajor

Without it, the build uses /usr/bin/ranlib, which, for some reason,
doesn't fail, but does weird things.

Differential Revision: https://phabricator.services.mozilla.com/D100073

taskcluster/scripts/misc/build-compiler-rt.sh

@@ -26,6 +26,7 @@ cmake \
   -DCMAKE_LINKER=$MOZ_FETCHES_DIR/cctools/bin/aarch64-apple-darwin-ld \
   -DCMAKE_LIPO=$MOZ_FETCHES_DIR/cctools/bin/lipo \
   -DCMAKE_AR=$MOZ_FETCHES_DIR/cctools/bin/aarch64-apple-darwin-ar \
+  -DCMAKE_RANLIB=$MOZ_FETCHES_DIR/cctools/bin/aarch64-apple-darwin-ranlib \
   -DCMAKE_BUILD_TYPE=Release \
   -DLLVM_ENABLE_ASSERTIONS=OFF \
   -DLLVM_CONFIG_PATH=$MOZ_FETCHES_DIR/clang/bin/llvm-config \