efivar: ensure that target security flags are not used to build native code

Also set LDFLAGS=BUILD_LDFLAGS when compiling makeguids to ensure that any
target compiler flags are not passed to the native compiler.

[ YOCTO #13423 ]

(From OE-Core rev: f61e0676aabba9e006c32f0e53c69426368cd4f0)

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

meta/recipes-bsp/efivar/efivar_37.bb

@@ -23,7 +23,10 @@ LDFLAGS += "-fuse-ld=bfd"
 
 do_compile_prepend() {
     # Remove when https://github.com/rhboot/efivar/issues/130 is fixed
-    oe_runmake CFLAGS="${BUILD_CFLAGS}" -C src makeguids
+    oe_runmake \
+        CFLAGS="${BUILD_CFLAGS}" \
+        LDFLAGS="${BUILD_LDFLAGS}" \
+        -C src makeguids
 }
 
 do_install() {