riscv : modify Makefile and add a RISCV_VECT to print log info (#9442)

- Added ggml_cpu_has_riscv_v() in GGML to print system info in log
- Modified Makefile to only use flag when cross compiling for RISC-V

ggml/src/ggml.c

@@ -23288,6 +23288,14 @@ int ggml_cpu_has_arm_fma(void) {
 #endif
 }
 
+int ggml_cpu_has_riscv_v(void) {
+#if defined(__riscv_v_intrinsic)
+    return 1;
+#else
+    return 0;
+#endif
+}
+
 int ggml_cpu_has_metal(void) {
 #if defined(GGML_USE_METAL)
     return 1;