mac: Keep libtool warning quiet with newer ld64s

Due to innovation in ld64's warning output, some non-interesting
warnings make it past our filters:

warning: /Applications/Xcode-beta.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/libtool:
    archive library: clang_x64_v8_arm64/obj/third_party/perfetto/protos/perfetto/common/libzero.a
    the table of contents is empty (no object file members in the library define global symbols)

Innovate right back.

Also make it clear which of these patterns span several lines.

Bug: none
Change-Id: I8542ab4d82005eaa67fae4a7af398ba1ebf8220f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2416830
Commit-Queue: Nico Weber <thakis@chromium.org>
Reviewed-by: Mark Mentovai <mark@chromium.org>
Auto-Submit: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#808021}

build/toolchain/mac/filter_libtool.py

@@ -12,21 +12,27 @@ import sys
 # This script executes libool and filters out logspam lines like:
 #    '/path/to/libtool: file: foo.o has no symbols'
 
-BLACKLIST_PATTERNS = [
+SUPPRESSED_PATTERNS = [
     re.compile(v) for v in [
         r'^.*libtool: (?:for architecture: \S* )?file: .* has no symbols$',
-        r'^.*libtool: warning for library: .* the table of contents is empty '
-        r'\(no object file members in the library define global symbols\)$',
-        r'^.*libtool: warning same member name \(\S*\) in output file used for '
-        r'input files: \S* and: \S* \(due to use of basename, truncation, '
-        r'blank padding or duplicate input files\)$',
+        # Xcode 11 spelling of the "empty archive" warning.
+        # TODO(thakis): Remove once we require Xcode 12.
+        r'^.*libtool: warning for library: .* the table of contents is empty ' \
+            r'\(no object file members in the library define global symbols\)$',
+        # Xcode 12 spelling of the "empty archive" warning.
+        r'^warning: .*libtool: archive library: .* ' \
+            r'the table of contents is empty ',
+            r'\(no object file members in the library define global symbols\)$',
+        r'^.*libtool: warning same member name \(\S*\) in output file used ' \
+            r'for input files: \S* and: \S* \(due to use of basename, ' \
+            r'truncation, blank padding or duplicate input files\)$',
     ]
 ]
 
 
-def IsBlacklistedLine(line):
+def ShouldSuppressLine(line):
   """Returns whether the line should be filtered out."""
-  for pattern in BLACKLIST_PATTERNS:
+  for pattern in SUPPRESSED_PATTERNS:
     if pattern.match(line):
       return True
   return False
@@ -37,7 +43,7 @@ def Main(cmd_list):
   libtoolout = subprocess.Popen(cmd_list, stderr=subprocess.PIPE, env=env)
   _, err = libtoolout.communicate()
   for line in err.decode('UTF-8').splitlines():
-    if not IsBlacklistedLine(line):
+    if not ShouldSuppressLine(line):
       print(line, file=sys.stderr)
   return libtoolout.returncode