[buildroot] do not pass optimization flags in HOST_CPPFLAGS (#12153)

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@33351 3c298f89-4303-0410-b956-a3cf2f4a3e73

include/host-build.mk

@@ -47,7 +47,7 @@ endef
 HOST_CONFIGURE_VARS = \
 	CC="$(HOSTCC)" \
 	CFLAGS="$(HOST_CFLAGS)" \
-	CPPFLAGS="$(HOST_CFLAGS)" \
+	CPPFLAGS="$(HOST_CPPFLAGS)" \
 	LDFLAGS="$(HOST_LDFLAGS)" \
 	SHELL="$(BASH)"
 

rules.mk

@@ -173,7 +173,8 @@ PKG_CONFIG:=$(STAGING_DIR_HOST)/bin/pkg-config
 export PKG_CONFIG
 
 HOSTCC:=gcc
-HOST_CFLAGS:=-O2 -I$(STAGING_DIR_HOST)/include
+HOST_CPPFLAGS:=-I$(STAGING_DIR_HOST)/include
+HOST_CFLAGS:=-O2 $(HOST_CPPFLAGS)
 HOST_LDFLAGS:=-L$(STAGING_DIR_HOST)/lib
 
 TARGET_CC:=$(TARGET_CROSS)gcc