GCC: disable -Wcomments.

-Wcomment gives too many false positives in the case a
backslash ended comment line is followed by a new line of
comments:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61638

Bug: 819294

Change-Id: I3c809aa7ce9f232775b58d153d45d81ad27880e4
Reviewed-on: https://chromium-review.googlesource.com/944409Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: José Dapena Paz <jose.dapena@lge.com>
Cr-Commit-Position: refs/heads/master@{#542155}

build/config/compiler/BUILD.gn

@@ -1278,6 +1278,12 @@ config("default_warnings") {
       # [1] https://gcc.gnu.org/gcc-6/porting_to.html#this-cannot-be-null
       # [2] https://crbug.com/784492#c13
       cflags += [ "-fno-delete-null-pointer-checks" ]
+
+      # -Wcomment gives too many false positives in the case a
+      # backslash ended comment line is followed by a new line of
+      # comments
+      # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61638
+      cflags += [ "-Wno-comments" ]
     }
   }