gyp: do not force stack protector on Chrome OS

build/common.gypi

Index: build/common.gypi
diff --git a/build/common.gypi b/build/common.gypi
index 01904f5478645cb3b9a1a1e6824584316948b86f..50983b81d92758f27be5f13be8ade63e4fb976da 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -2372,18 +2372,25 @@
   'conditions': [
     ['os_posix==1', {
       'target_defaults': {
-        'cflags': [
-          # TODO(phajdan.jr): Use -fstack-protector-strong when our gcc
-          # supports it.
-          '-fstack-protector',
-          '--param=ssp-buffer-size=4',
-        ],
         'ldflags': [
           '-Wl,-z,now',
           '-Wl,-z,relro',
         ],
       },
     }],
+    ['os_posix==1 and chromeos==0', {
+      # Chrome OS enables -fstack-protector-strong via its build wrapper,
+      # and we want to avoid overriding this, so stack-protector is only
+      # enabled when not building on Chrome OS.
+      # TODO(phajdan.jr): Use -fstack-protector-strong when our gcc
+      # supports it.
+      'target_defaults': {
+        'cflags': [
+          '-fstack-protector',
+          '--param=ssp-buffer-size=4',
+        ],
+      },
+    }],
     ['os_posix==1 and OS!="mac" and OS!="ios"', {
       'target_defaults': {
         # Enable -Werror by default, but put it in a variable so it can