[build] Use macOS specific settings only for macOS builds

Fixes #143

Author: lpinca

binding.gyp

@@ -4,11 +4,15 @@
       'target_name': 'bufferutil',
       'sources': ['src/bufferutil.c'],
       'cflags': ['-std=c99'],
-      'xcode_settings': {
-        'MACOSX_DEPLOYMENT_TARGET': '10.7',
-        'OTHER_CFLAGS': ['-arch x86_64', '-arch arm64'],
-        'OTHER_LDFLAGS': ['-arch x86_64', '-arch arm64']
-      }
+      'conditions': [
+        ["OS=='mac'", {
+          'xcode_settings': {
+            'MACOSX_DEPLOYMENT_TARGET': '10.7',
+            'OTHER_CFLAGS': ['-arch x86_64', '-arch arm64'],
+            'OTHER_LDFLAGS': ['-arch x86_64', '-arch arm64']
+          }
+        }]
+      ]
     }
   ]
 }