recognize riscv as a cpu model

Author: Kalamatee

external/openurl/cmd/version.h

@@ -68,6 +68,10 @@
   #define CPU "x86"
 #elif defined(__x86_64__)
   #define CPU "x86_64"
+#elif defined(__riscv64)
+  #define CPU "RISC-V 64bit"
+#elif defined(__riscv)
+  #define CPU "RISC-V"
 #elif defined(__arm__)
   #define CPU "ARM"
 #else