[yocto] [PATCH][meta-mingw] mingw32-common: only export WINDRES/RC for SDK build

[changqing.li at windriver.com]

From: Changqing Li <changqing.li at windriver.com>

Fix below problem:
MACHINE=intel-x86-64
SDKMACHINE = "i686-mingw32"
bitbake freetype

do_compile failed with below error:
x86_64-wrs-linux-libtool: compile:  x86_64-wrs-linux-windres
--include-dir=work/corei7-64-wrs-linux/freetype/2.9.1-r0/recipe-sysroot/usr/include
/work/corei7-64-wrs-linux/freetype/2.9.1-r0/freetype-2.9.1/src/base/ftver.rc
-o work/corei7-64-wrs-linux/freetype/2.9.1-r0/build/.libs/ftver.o
work/corei7-64-wrs-linux/freetype/2.9.1-r0/build//x86_64-wrs-linux-libtool:
line 1752: x86_64-wrs-linux-windres: command not found

we don't want to use windres for target build, only export WINDRES/RC when build
SDK. SDK_OS = "mingw32", so use this override to fix it.

Signed-off-by: Changqing Li <changqing.li at windriver.com>
---
 conf/machine-sdk/include/mingw32-common.inc | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/conf/machine-sdk/include/mingw32-common.inc b/conf/machine-sdk/include/mingw32-common.inc
index 07b103a..92bd184 100644
--- a/conf/machine-sdk/include/mingw32-common.inc
+++ b/conf/machine-sdk/include/mingw32-common.inc
@@ -28,8 +28,11 @@ SDKPKGSUFFIX = "nativesdk-mingw32"
 
 MACHINEOVERRIDES .= ":sdkmingw32"
 
-export WINDRES = "${HOST_PREFIX}windres --include-dir=${STAGING_INCDIR}"
-export RC = "${WINDRES}"
+WINDRES_mingw32 = "${HOST_PREFIX}windres --include-dir=${STAGING_INCDIR}"
+RC_mingw32 = "${WINDRES}"
+
+export WINDRES
+export RC
 
 BB_HASHBASE_WHITELIST_append = " WINDRES RC"
 
-- 
2.7.4