GYP build: Provide automatic host_arch detection on Mac

build/standalone.gypi

Index: build/standalone.gypi
diff --git a/build/standalone.gypi b/build/standalone.gypi
index f104d08c197b4d1ba515541a63a6020bfd1e36d5..ebdf55723030ee8fb1af1f19fa8460bc94235fda 100644
--- a/build/standalone.gypi
+++ b/build/standalone.gypi
@@ -37,8 +37,9 @@
       'variables': {
         'variables': {
           'conditions': [
-            ['OS=="linux" or OS=="freebsd" or OS=="openbsd" or OS=="netbsd"', {
-              # This handles the Linux platforms we generally deal with.
+            ['OS=="linux" or OS=="freebsd" or OS=="openbsd" or \
+               OS=="netbsd" or OS=="mac"', {
+              # This handles the Unix platforms we generally deal with.
               # Anything else gets passed through, which probably won't work
               # very well; such hosts should pass an explicit target_arch
               # to gyp.
@@ -46,7 +47,8 @@
                 '<!(uname -m | sed -e "s/i.86/ia32/;\
                   s/x86_64/x64/;s/amd64/x64/;s/arm.*/arm/;s/mips.*/mips/")',
             }, {
-              # OS!="linux" and OS!="freebsd" and OS!="openbsd" and OS!="netbsd"
+              # OS!="linux" and OS!="freebsd" and OS!="openbsd" and
+              # OS!="netbsd" and OS!="mac"
               'host_arch%': 'ia32',
             }],
           ],