arm: better stub version for MISMATCH_CHECK

stub version of MISMATCH_CHECK is empty so it's easy to misuse for
people not building kvm on arm.  Use QEMU_BUILD_BUG_ON similar to the
non-stub version to make it easier to catch bugs.
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>
Reviewed-by: NPeter Maydell <peter.maydell@linaro.org>

target/arm/kvm-consts.h

@@ -21,7 +21,9 @@
 #define MISMATCH_CHECK(X, Y) QEMU_BUILD_BUG_ON(X != Y)
 
 #else
-#define MISMATCH_CHECK(X, Y)
+
+#define MISMATCH_CHECK(X, Y) QEMU_BUILD_BUG_ON(0)
+
 #endif
 
 #define CP_REG_SIZE_SHIFT 52