gcc: fix run environment variables not being exported in environments (#41729)

Since views use symlinks, all compiler binaries were skipped in this
case. Instead, only skip them if their target does not exist.

var/spack/repos/builtin/packages/gcc/package.py

@@ -1016,7 +1016,9 @@ def setup_run_environment(self, env):
                     continue
 
                 abspath = os.path.join(bin_path, filename)
-                if os.path.islink(abspath):
+
+                # Skip broken symlinks (https://github.com/spack/spack/issues/41327)
+                if not os.path.exists(abspath):
                     continue
 
                 # Set the proper environment variable