CI: Add code coverage mesurement for powerpc-unknown-linux-gnu.

Profiler builtins were added in
rust-lang/rust#119404.

.github/workflows/ci.yml

@@ -472,7 +472,7 @@ jobs:
           - i686-unknown-linux-gnu         # Has assembly
           # TODO: arm-unknown-linux-gnueabi # Has assembly but doesn't build w/ clang
           # TODO: armv7-unknown-linux-gnueabihf # Has assembly but doesn't have profiler builtins
-          # TODO: powerpc-unknown-linux-gnu  No assembly 32-bit big-endian but doesn't have profiler builtins
+          - powerpc-unknown-linux-gnu      # No assembly 32-bit big-endian with flags
           - powerpc64-unknown-linux-gnu    # No assembly 64-bit big-endian with flags
           - powerpc64le-unknown-linux-gnu  # No assembly 64-bit little-endian with flags
           - riscv64gc-unknown-linux-gnu    # No assembly 64-bit little-endian without flags