CHROMIUMOS: Compile with -fPIE.

Otherwise the tests fail to build in the chromium-os environment.

BUG=None
TEST='FEATURES=test emerge' on x86-zgb and amd64-corei7
     'emerge' on arm-generic

Change-Id: I24a4ddbfd113609f7fbc185b7660ee3b7387fbbf
diff --git a/build_detect_platform b/build_detect_platform
index 5f9e021..722972f 100644
--- a/build_detect_platform
+++ b/build_detect_platform
@@ -61,8 +61,8 @@
 
 echo "PLATFORM=$PLATFORM" >> build_config.mk
 
-# On GCC, use libc's memcmp, not GCC's memcmp
-PORT_CFLAGS="-fno-builtin-memcmp"
+# On GCC, use libc's memcmp, not GCC's memcmp; and use PIE
+PORT_CFLAGS="-fno-builtin-memcmp -fPIE"
 
 # Detect C++0x -- this determines whether we'll use port_noatomic.h
 # or port_posix.h by: