Silence shift-negative-value warnings only on POSIX/Clang.

third_party/third_party.gyp

 # Copyright 2014 PDFium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 {
   'variables': {
     'pdf_enable_xfa%': 0,  # Set to 1 by standalone.gypi in standalone builds.
   },
   'target_defaults': {
     'defines': [
@@ skipping 212 matching lines @@
         'libjpeg/jdhuff.h',
         'libjpeg/jerror.h',
         'libjpeg/jinclude.h',
         'libjpeg/jmemsys.h',
         'libjpeg/jmorecfg.h',
         'libjpeg/jpegint.h',
         'libjpeg/jpeglib.h',
         'libjpeg/jversion.h',
         'libjpeg/transupp.h',
       ],
-      'cflags': [
-        '-Wno-shift-negative-value',
-      ],
       'conditions': [
         ['os_posix==1', {
           'cflags': [
             '-Wno-main',
             '-Wno-missing-braces',
+            '-Wno-shift-negative-value',
             '-Wno-unused',
           ],
         }],
       ],
     },
     {
       'target_name': 'fx_libopenjpeg',
       'type': 'static_library',
       'sources': [
         'libopenjpeg20/bio.c',
@@ skipping 58 matching lines @@
         'zlib_v128/gzread.c',
         'zlib_v128/gzwrite.c',
         'zlib_v128/infback.c',
         'zlib_v128/inffast.c',
         'zlib_v128/inflate.c',
         'zlib_v128/inftrees.c',
         'zlib_v128/trees.c',
         'zlib_v128/uncompr.c',
         'zlib_v128/zutil.c',
       ],
-      'cflags': [
-        # TODO(dsinclair): Remove if fixed upstream. https://crbug.com/507712
-        '-Wno-shift-negative-value',
+      'conditions': [
+        ['os_posix==1', {
+          'cflags': [
+            # TODO(dsinclair): Remove if fixed upstream. https://crbug.com/507712
+            '-Wno-shift-negative-value',
+          ],
+        }],
       ],
 
     },
     {
       'target_name': 'pdfium_base',
       'type': 'none',
       'sources': [
         'base/logging.h',
         'base/macros.h',
         'base/numerics/safe_conversions.h',
@@ skipping 47 matching lines @@
             'libtiff/tif_version.c',
             'libtiff/tif_warning.c',
             'libtiff/tif_write.c',
             'libtiff/tif_zip.c',
           ],
         },
       ],
     }],
   ],
 }