crossgcc: Enable multiple targets for a platform

This is required on powerpc64 to build both little endian and big endian
libgcc.

Change-Id: I295c8ee5e8131d4108e98d1bfd53abb8bd8982b2
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Reviewed-on: https://review.coreboot.org/14163
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

util/crossgcc/buildgcc

@@ -450,7 +450,7 @@ build_GCC() {
 		--disable-libssp --disable-bootstrap --disable-nls \
 		--disable-libquadmath --without-headers \
 		--disable-threads \
-		--enable-interwork --enable-multilib \
+		--enable-interwork --enable-multilib --enable-targets=all \
 		--disable-libatomic --disable-libcc1 --disable-decimal-float \
 		${GCC_OPTIONS} --enable-languages="${LANGUAGES}" \
 		--with-system-zlib \