libffi: fix native build being not portable

Without `--with-gcc-arch=generic` libffi looks up the cpuid to automatically determine
which mtune/march to use. This makes the native sstate-cache unuseable since it's
possible to have a newer cpu building the recipe and the library being pulled from
another older cpu which doesn't have the instruction.

(From OE-Core rev: cddaecac1fdd4d033c2ff8ccaf1d60e1c598d5b7)

Signed-off-by: Maxime Roussin-Bélanger <maxime.roussinbelanger@gmail.com>
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-support/libffi/libffi_3.4.2.bb

@@ -19,6 +19,7 @@ UPSTREAM_CHECK_URI = "https://github.com/libffi/libffi/releases/"
 UPSTREAM_CHECK_REGEX = "libffi-(?P<pver>\d+(\.\d+)+)\.tar"
 
 EXTRA_OECONF += "--disable-builddir --disable-exec-static-tramp"
+EXTRA_OECONF:class-native += "--with-gcc-arch=generic"
 EXTRA_OEMAKE:class-target = "LIBTOOLFLAGS='--tag=CC'"
 inherit autotools texinfo multilib_header
 
@@ -33,4 +34,3 @@ FILES:${PN}-dev += "${libdir}/libffi-${PV}"
 MIPS_INSTRUCTION_SET = "mips"
 
 BBCLASSEXTEND = "native nativesdk"
-