linux-libc-headers: allow overriding compiler name in KConfig

The KConfig infrastructure needs to build HOST binaries in order to
provide its infratstructure. Yocto needs to force the HOSTCC and HOSTCPP
variables to BUILD_CC and BUILD_CPP to make sure that the proper compiler
is used when compiling host binaries

(From OE-Core rev: 4676525795c565855cadd992e4be68eba6bc8b01)

Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-kernel/linux-libc-headers/linux-libc-headers.inc

@@ -50,6 +50,8 @@ SRC_URI = "${KERNELORG_MIRROR}/linux/kernel/v${HEADER_FETCH_VER}/linux-${PV}.tar
 
 S = "${WORKDIR}/linux-${PV}"
 
+EXTRA_OEMAKE = " HOSTCC="${BUILD_CC}" HOSTCPP="${BUILD_CPP}""
+
 do_configure() {
 	oe_runmake allnoconfig
 }