fix #1246 (#1254)

* fix finding python path which only has python3.

* fix #1246, arm host issue.

* skip assembler tests on non-x86 host.

* update macro of dummy value.

* fix MSVC macro.

* update dummy array value macro.

* restore to original qemu code.

tests/unit/test_pc_change.c

@@ -57,6 +57,9 @@ static void test_pc_change(void **state)
     int32_t r_ecx = 3, r_edx = 15;
     struct stat info;
     char *code = read_file("pc_change.bin", &info);
+    if (code == NULL) {
+        return;
+    }
 
 #define BASEADDR    0x1000000