[Buildroot] [PATCH v2, 1/1] package/libkcapi: fix build with BR2_OPTIMIZE_0

[Fabrice Fontaine]

Override CPPFLAGS to fix the following build failure with BR2_OPTIMIZE_0
raised since bump to version 0.14.0 in commit
cd707a9112e38b4ce98326b96c0ed12054ca1cca and
https://github.com/smuellerDD/libkcapi/commit/0e7b2b0300782aca19c324f3352f109777b4c51a:

/home/autobuild/autobuild/instance-15/output-1/host/i686-buildroot-linux-gnu/sysroot/usr/include/features.h:412:4: error: #warning _FORTIFY_SOURCE requires compiling with optimization (-O) [-Werror=cpp]

It should be noted that upstream already rejected a PR to remove
-Werror: https://github.com/smuellerDD/libkcapi/pull/132

Fixes:
 - http://autobuild.buildroot.org/results/35141ea3046f5a4593e0b27ef92e4ace6bc0be66

Signed-off-by: Fabrice Fontaine <fontaine.fabrice at gmail.com>
---
Changes v1 -> v2 (after review of Arnout Vandecappelle):
 - Override CPPFLAGS instead of COMMON_CPPFLAGS as -D_FORTIFY_SOURCE=2
   is added to CPPFLAGS by ax_add_fortify_source.m4

 package/libkcapi/libkcapi.mk | 1 +
 1 file changed, 1 insertion(+)

diff --git a/package/libkcapi/libkcapi.mk b/package/libkcapi/libkcapi.mk
index 71dfbd9eff..30d500696b 100644
--- a/package/libkcapi/libkcapi.mk
+++ b/package/libkcapi/libkcapi.mk
@@ -15,6 +15,7 @@ LIBKCAPI_CONF_ENV = \
 	ac_cv_path_DB2PDF="" \
 	ac_cv_path_DB2PS="" \
 	ac_cv_path_XMLTO=""
+LIBKCAPI_MAKE_OPTS = CPPFLAGS="$(TARGET_CPPFLAGS)"
 
 ifeq ($(BR2_PACKAGE_LIBKCAPI_ENCAPP),y)
 LIBKCAPI_CONF_OPTS += --enable-kcapi-encapp
-- 
2.35.1