efivar: fix build when host gcc version is < 4.9

efivar v27 started using C11 _Generic keyword in macros but that
is not implemented in gcc until 4.9. This makes efivar-native
(which is a dependency to efivar) build to fail if the builder host
gcc version is < 4.9.

It turns out only 'makeguids' generator needs to be built for the
build arch to generate GENERATED_SOURCES for efivar target build.
'makeguids' sources/includes have no gcc version dependencies so
to fix efivar build when host gcc < 4.9, we simply build 'makeguids'
target for efivar-native.

Signed-off-by: Mikko Ylinen <mikko.ylinen@linux.intel.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>

meta-oe/recipes-extended/efivar/efivar_0.31.bb

@@ -35,11 +35,15 @@ do_compile_prepend() {
     sed -i -e s:-Werror::g ${S}/gcc.specs
 }
 
+do_compile_class-native() {
+    oe_runmake -C src makeguids
+}
+
 do_install() {
     oe_runmake install DESTDIR=${D}
 }
 
-do_install_append_class-native() {
+do_install_class-native() {
     install -D -m 0755 ${B}/src/makeguids ${D}${bindir}/makeguids
 }