Automated rollback of commit 1b4c37c.

*** Reason for rollback ***

Breaks protobuf when bootstrapping bazel (#7605)

ERROR: /home/bazel/.cache/bazel/_bazel_bazel/ec321eb2cc2d0f8f91b676b6d4c66c29/external/io_bazel/third_party/protobuf/3.6.1/BUILD:123:1: undeclared inclusion(s) in rule '@io_bazel//third_party/protobuf/3.6.1:protobuf_lite':
this rule is missing dependency declarations for the following files included by 'external/io_bazel/third_party/protobuf/3.6.1/src/google/protobuf/stubs/bytestream.cc':
  '/workdir/third_party/protobuf/3.6.1/src/google/protobuf/stubs/bytestream.h'
  '/workdir/third_party/protobuf/3.6.1/src/google/protobuf/stubs/common.h'
  '/workdir/third_party/protobuf/3.6.1/src/google/protobuf/stubs/port.h'
  '/workdir/third_party/protobuf/3.6.1/src/google/protobuf/stubs/platform_macros.h'
  '/workdir/third_party/protobuf/3.6.1/src/google/protobuf/stubs/macros.h'
  '/workdir/third_party/protobuf/3.6.1/src/google/protobuf/stubs/logging.h'
  '/workdir/third_party/protobuf/3.6.1/src/google/protobuf/stubs/mutex.h'
  '/workdir/third_party/protobuf/3.6.1/src/google/protobuf/stubs/callback.h'
  '/workdir/third_party/protobuf/3.6.1/src/google/protobuf/stubs/stringpiece.h'
  '/workdir/third_party/protobuf/3.6.1/src/google/protobuf/stubs/hash.h'

*** Original change description ***

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: 236613108

tools/cpp/unix_cc_configure.bzl

@@ -202,21 +202,20 @@ 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 '-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.
+    # 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.
     opt = _add_compiler_option_if_supported(
         repository_ctx,
         cc,
-        "-no-canonical-prefixes",
+        "-fno-canonical-system-headers",
     )
     if len(opt) == 0:
         return _add_compiler_option_if_supported(
             repository_ctx,
             cc,
-            "-fno-canonical-system-headers",
+            "-no-canonical-prefixes",
         )
     return opt