For consistency, use our homebrew zlib everywhere possible.

gyp/zlib.gyp

Index: gyp/zlib.gyp
diff --git a/gyp/zlib.gyp b/gyp/zlib.gyp
index 7ae62309d25f50939ebe924c940c94491fd9b5a8..7d2eb785805ce57ae2cedbcda79375b19046e6cb 100644
--- a/gyp/zlib.gyp
+++ b/gyp/zlib.gyp
@@ -4,45 +4,47 @@
 # found in the LICENSE file.
 
 {
+  'variables': {
+    'skia_warnings_as_errors': 0,
+  },
   'targets': [
   {
-    # Only used by win, down below.
     'target_name' : 'zlib_x86_simd',
     'type': 'static_library',
     'cflags' : ['-msse4.2', '-mpclmul'],
+    'xcode_settings': {
+        'OTHER_CFLAGS': ['-msse4.2', '-mpclmul'],
+    },
     'sources' : [
+      '../third_party/externals/zlib/x86.h',
+      '../third_party/externals/zlib/x86.c',
       '../third_party/externals/zlib/crc_folding.c',
       '../third_party/externals/zlib/fill_window_sse.c',
     ],
-      'conditions': [
-        ['skia_clang_build==1', {
-          'msvs_settings': {
-            'VCCLCompilerTool': {
-              'AdditionalOptions': [ '-msse4.2', '-mpclmul' ],
-            },
+    'conditions': [
+      ['skia_clang_build==1', {
+        'msvs_settings': {
+          'VCCLCompilerTool': {
+            'AdditionalOptions': [ '-msse4.2', '-mpclmul' ],
           },
-        }],
-      ],
+        },
+      }],
+      ['skia_os in ["linux", "chromeos"]', {
+        'all_dependent_settings': {
+          'libraries': [ '-lpthread' ],
+        },
+      }],
+    ],
   },
   {
       'target_name': 'zlib',
-      'direct_dependent_settings': {
-        'conditions': [
-          [ 'skia_android_framework', { 'include_dirs': [ 'external/zlib' ] }],
-          [ 'skia_os == "mac" or skia_os == "ios"', {
-              # XCode needs and explicit file path, not a logical name like -lz.
-              'link_settings': { 'libraries': [ '$(SDKROOT)/usr/lib/libz.dylib' ] },
-          }],
-          [ 'skia_os not in ["mac", "ios", "win"]',{
-              'link_settings': { 'libraries': [ '-lz' ] },
-          }]
-        ],
-      },
       'conditions': [
-        [ 'skia_os != "win"', {
-          'type': 'none',
-        }, {
-          # win
+        [ 'skia_android_framework', {
+            'type': 'none',
+            'direct_dependent-settings': {
+                'include_dirs': [ 'external/zlib' ]
+            },
+        },{
           'type': 'static_library',
           'sources': [
             '../third_party/externals/zlib/adler32.c',
@@ -68,8 +70,6 @@
             '../third_party/externals/zlib/trees.c',
             '../third_party/externals/zlib/trees.h',
             '../third_party/externals/zlib/uncompr.c',
-            '../third_party/externals/zlib/x86.h',
-            '../third_party/externals/zlib/x86.c',
             '../third_party/externals/zlib/zconf.h',
             '../third_party/externals/zlib/zlib.h',
             '../third_party/externals/zlib/zutil.c',
@@ -83,8 +83,12 @@
               '../third_party/externals/zlib',
             ],
           },
-          'dependencies': [
-            'zlib_x86_simd',
+          'conditions': [
+            [ '"x86" in skia_arch_type', {
+              'dependencies': [ 'zlib_x86_simd' ],
+            },{
+              'sources': ['../third_party/externals/zlib/simd_stub.c'],
+            }]
           ],
           'defines': [
             '_CRT_NONSTDC_NO_DEPRECATE',