Switch optimization cflag to late-resolve the debug_optimize and release_optimize vars.

This will allow lower-level targets to change their desired optimization level.  In particular, the ffmpeg build requires this because it has problems compiling with -O0.

BUG=22307
TEST=none

Review URL: http://codereview.chromium.org/334018

git-svn-id: http://src.chromium.org/svn/trunk/src/build@30110 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

common.gypi

@@ -579,7 +579,7 @@
               '_DEBUG',
             ],
             'cflags': [
-              '-O<(debug_optimize)',
+              '-O>(debug_optimize)',
               '-g',
               # One can use '-gstabs' to enable building the debugging
               # information in STABS format for breakpad's dumpsyms.
@@ -593,7 +593,7 @@
               'release_optimize%': '2',
             },
             'cflags': [
-              '-O<(release_optimize)',
+              '-O>(release_optimize)',
               # Don't emit the GCC version ident directives, they just end up
               # in the .comment section taking up binary size.
               '-fno-ident',