Correct the env.cc reference

.github/workflows/build.yaml

@@ -218,7 +218,7 @@ jobs:
         if [[ '${{ matrix.qt }}' =~ ^(5|6\.[01])\. ]]; then arch=x86_64
         # GitHub runners' (homebrew'd) gcc's only support support x86-64 prior to macos-14, and only arm64 after.
         # Note: if we attempt to use multiple archs, gcc will warn, but continue, resulting in later failures.
-        elif [[ '${{ matrix.cc }}' == gcc-* ]]; then
+        elif [[ '${{ matrix.env.cc }}' == gcc-* ]]; then
           if [[ '${{ matrix.os }}' == 'macos-13' ]]; then arch='x86_64'; else arch='arm64'; fi
         # Otherwise, default to universal binaries, where possible.
         else arch='arm64;x86_64'; fi