Revert "Revert CFLAGS changes in Makefile."

This reverts commit 66fc895ad76ce5854fa98b910c383bc04f942572.
The net-wireless/gdmwimax ebuild is changed to compile the gdmwimax
source code without FORTIFY_SOURCE.

BUG=chrome-os-partner:10133
TEST=Manually test connecting to a WiMAX network.

Change-Id: Ia951dc9d91760a4f4c96f4bbf8daf958a767dbf0
Reviewed-on: https://gerrit.chromium.org/gerrit/24326
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Tested-by: Ben Chan <benchan@chromium.org>
Commit-Ready: Ben Chan <benchan@chromium.org>
diff --git a/cm/Makefile b/cm/Makefile
index 670b0fb..0e4f7e2 100644
--- a/cm/Makefile
+++ b/cm/Makefile
@@ -12,7 +12,7 @@
 
 .EXPORT_ALL_VARIABLES:
 
-CFLAGS = -g -O0
+CFLAGS ?= -g -O2
 CFLAGS += -Wall
 
 ifeq ("$(CONFIG_DM_INTERFACE)", "y")
diff --git a/sdk/Makefile b/sdk/Makefile
index df223eb..f31ae61 100644
--- a/sdk/Makefile
+++ b/sdk/Makefile
@@ -12,7 +12,7 @@
 
 .EXPORT_ALL_VARIABLES:
 
-CFLAGS = -g -O0
+CFLAGS ?= -g -O2
 CFLAGS += -Wall -fPIC
 
 ifeq ("$(CONFIG_TRANSPORT_TEST)", "y")