sparc64: fix toolchain building when C++ is enabled

Disable libsanitizer for sparc64, too. Same problem as for
sparc, see https://bugs.busybox.net/show_bug.cgi?id=7951

Reported-By: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Waldemar Brodkorb <wbx@openadk.org>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/gcc/gcc.mk

@@ -142,7 +142,7 @@ endif
 
 # libsanitizer is broken for SPARC
 # https://bugs.busybox.net/show_bug.cgi?id=7951
-ifeq ($(BR2_sparc),y)
+ifeq ($(BR2_sparc)$(BR2_sparc64),y)
 HOST_GCC_COMMON_CONF_OPTS += --disable-libsanitizer
 endif