Move werror variable declation to non-conditional block.

build/common.gypi

Index: build/common.gypi
diff --git a/build/common.gypi b/build/common.gypi
index 74e88377091117cc82f22df6985e1ab453657649..ca1e32ca6691540cd4e9c09177dca7caa0c2fe85 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -674,6 +674,12 @@
     'google_default_client_id%': '<(google_default_client_id)',
     'google_default_client_secret%': '<(google_default_client_secret)',
 
+    # Enable -Werror by default, but put it in a variable so it can
+    # be disabled (e.g. in ~/.gyp/include.gypi on the valgrind builders).
+    # This is needed on all platforms since it is used when building
+    # NaCl untrusted code.
+    'werror%': '-Werror',
+
     # Use system protobuf instead of bundled one.
     'use_system_protobuf%': 0,
 
@@ -2208,10 +2214,7 @@
   'conditions': [
     ['os_posix==1 and OS!="mac" and OS!="ios"', {
       'target_defaults': {
-        # Enable -Werror by default, but put it in a variable so it can
-        # be disabled in ~/.gyp/include.gypi on the valgrind builders.
         'variables': {
-          'werror%': '-Werror',
           'libraries_for_target%': '',
         },
         'defines': [