Always set --no-canonical-prefixes if we can

-no-canonical-prefixes should be enough in all cases except very
old compilers. For those, we keep using -fno-canonical-system-headers

Closes #7316.

PiperOrigin-RevId: 234574545

tools/cpp/unix_cc_configure.bzl

@@ -202,20 +202,21 @@ def _get_no_canonical_prefixes_opt(repository_ctx, cc):
  # If the compiler sometimes rewrites paths in the .d files without symlinks
  # (ie when they're shorter), it confuses Bazel's logic for verifying all
  # #included header files are listed as inputs to the action.
+ # We also rely on symlinks not being resolved for remote builds.
 
- # The '-fno-canonical-system-headers' should be enough, but clang does not
- # support it, so we also try '-no-canonical-prefixes' if first option does
- # not work.
+ # The '-no-canonical-prefixes' flag is enough in most cases.
+ # In case this flag is not supported (older gcc versions), we try to add
+ # '-fno-canonical-system-headers' instead.
  opt = _add_compiler_option_if_supported(
  repository_ctx,
  cc,
- "-fno-canonical-system-headers",
+ "-no-canonical-prefixes",
  )
  if len(opt) == 0:
  return _add_compiler_option_if_supported(
  repository_ctx,
  cc,
- "-no-canonical-prefixes",
+ "-fno-canonical-system-headers",
  )
  return opt