Improve comment about implicit-function-declaration

Author: eregon

.github/workflows/build.yml

@@ -77,7 +77,7 @@ jobs:
         fi
     - run: rm -rf $PREFIX
 
-    # macOS runners seem to default to -Werror=implicit-function-declaration, but extconf.rb expects it to be not fatal
+    # Apple clang defaults to -Werror=implicit-function-declaration, but extconf.rb expects it to be not fatal
     # See https://bugs.ruby-lang.org/issues/17777 for 2.6.7
     - name: Set warnflags for Ruby <= 2.2
       run: echo "warnflags=-Wno-error=implicit-function-declaration" >> $GITHUB_ENV