[ios fuzzing] Build Release build of macOS WebKit

Update compile_webkit_mac_minibrowser target to build release build.
WebKit folks recommended fuzzing release build to avoid hitting
assertions, which mostly indicate minor problems, which are not high
priority to fix.

Bug: 1064181
Change-Id: Ifdb22e20dc67b353b9ec237d63a40347dd7d7ecb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2129086Reviewed-by: Ali Juma <ajuma@chromium.org>
Commit-Queue: Eugene But <eugenebut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#754977}

ios/third_party/webkit/BUILD.gn

@@ -102,6 +102,7 @@ if (_build_custom_webkit) {
     ]
     args = [
       "--ios-simulator",
+      "--debug",
       "--output_dir",
       rebase_path("$_webkit_ios_out_base_dir"),
     ]

ios/third_party/webkit/build_webkit.py

@@ -17,6 +17,8 @@ def main():
                       help='Use "iphoneos" SDK instead of "macos".')
   parser.add_argument('--asan', action='store_true', default=False,
                       help='Make Asan build.')
+  parser.add_argument('--debug', action='store_true', default=False,
+                      help='Make debug build.')
   parser.add_argument('-j',
                     help='Number of parallel jobs to run.')
   (opts, extra_args) = parser.parse_known_args()
@@ -29,11 +31,14 @@ def main():
       '../../..',
       'out', 'Debug-iphonesimulator', 'obj', 'ios', 'third_party', 'webkit'));
 
-  command = ['src/Tools/Scripts/build-webkit', '--debug']
+  command = ['src/Tools/Scripts/build-webkit']
 
   if opts.ios_simulator:
     command.append('--ios-simulator')
 
+  if opts.debug:
+    command.append('--debug')
+
   if opts.j:
     command.extend(['-jobs', opts.j])
   command.extend(extra_args)
@@ -42,7 +47,9 @@ def main():
   cwd = os.path.dirname(os.path.realpath(__file__))
 
   if opts.asan:
-     config_command = ['src/Tools/Scripts/set-webkit-configuration', '--debug', '--asan']
+     config_command = ['src/Tools/Scripts/set-webkit-configuration', '--asan']
+     if opts.debug:
+       config_command.append('--debug')
      proc = subprocess.Popen(config_command, cwd=cwd, env=env)
      proc.communicate()
      if proc.returncode: