MDEV-34195 tests: avoid LP64 MYSQL size assert on x32

x32 defines __x86_64__ but uses the ILP32 ABI, so the LP64
sizeof(MYSQL) == 1272 compile-time assert is selected incorrectly
and breaks the build.

Guard the x86_64 check with !defined(__ILP32__) so the LP64 size assert
only applies to real amd64 LP64 builds, while leaving the existing
Windows amd64 and i386 checks unchanged.

Author: aquilamacedo

tests/mysql_client_fw.c

@@ -1440,7 +1440,7 @@ int main(int argc, char **argv)
 */
 #if defined _M_AMD64
   compile_time_assert(sizeof(MYSQL) == 1208);
-#elif defined __x86_64__
+#elif defined(__x86_64__) && !defined(__ILP32__)
   compile_time_assert(sizeof(MYSQL) == 1272);
 #elif defined __i386__
   compile_time_assert(sizeof(MYSQL) == 964);