[test-suite][CSKY] Add Architecture Detection for C-SKY

[zixuan-wu]

Summary

The LLVM test suite has its own way of detecting the system
architecture. This adds support in that file for detecting C-SKY.

[luismarques]

I'm not the best person to review test-suite patches, but I also don't see how this could be wrong, so I'm approving it.

cmake/modules/DetectArchitecture.c

 #elif defined(__sparc__)
 const char *str = "ARCHITECTURE IS Sparc";
 #elif defined(__xcore__)
 const char *str = "ARCHITECTURE IS XCore";
 #elif defined(__i386__) || defined(__x86_64__)
 const char *str = "ARCHITECTURE IS x86";
 #elif defined(__hexagon__)
 const char *str = "ARCHITECTURE IS Hexagon";
+#elif defined(__csky__) || defined(__CSKY__)
+const char *str = "ARCHITECTURE IS CSKY";
 #endif
 
 int main(int argc, char **argv) {
     int require = str[argc];
     (void)argv;
     return require;
 }