[source] build: properly pass CPP and CXX flags in HOST_MAKE_VARS

[LEDE Commits]

jow pushed a commit to source.git, branch master:
https://git.lede-project.org/5faad30d5da9d52d5e2198c695f58ad8eff4c3d4

commit 5faad30d5da9d52d5e2198c695f58ad8eff4c3d4
Author: Jo-Philipp Wich <jo at mein.io>
AuthorDate: Tue Jan 17 09:29:50 2017 +0100

    build: properly pass CPP and CXX flags in HOST_MAKE_VARS
    
    Signed-off-by: Jo-Philipp Wich <jo at mein.io>
---
 include/host-build.mk | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/host-build.mk b/include/host-build.mk
index c54ee37..70bf6e5 100644
--- a/include/host-build.mk
+++ b/include/host-build.mk
@@ -69,7 +69,8 @@ HOST_CONFIGURE_ARGS = \
 
 HOST_MAKE_VARS = \
 	CFLAGS="$(HOST_CFLAGS)" \
-	CXXFLAGS="$(HOST_CPPFLAGS)" \
+	CPPFLAGS="$(HOST_CPPFLAGS)" \
+	CXXFLAGS="$(HOST_CXXFLAGS)" \
 	LDFLAGS="$(HOST_LDFLAGS)"
 
 HOST_MAKE_FLAGS =