Add -Werror compile flag.

Change-Id: I58a4993aa91f91d1a5dc334a6ab98d0d633cc607

BUG=chromium-os:13802
TEST=still compiles under emerge-x86-mario and emerge-arm-generic

Review URL: http://codereview.chromium.org/6816005
diff --git a/SConstruct b/SConstruct
index db4ab37..1f5fbe7 100644
--- a/SConstruct
+++ b/SConstruct
@@ -15,7 +15,7 @@
   value = os.environ.get(key)
   if value != None:
     env[key] = Split(value)
-env['CCFLAGS'] += ['-fPIC', '-fno-exceptions', '-Wall']
+env['CCFLAGS'] += ['-fPIC', '-fno-exceptions', '-Wall', '-Werror']
 
 # Fix issue with scons not passing some vars through the environment.
 for key in Split('PKG_CONFIG_LIBDIR PKG_CONFIG_PATH SYSROOT'):