Support both -h, --help on spirv-as, spirv-val

The spirv-dis command already supports both.

tools/as/as.cpp

@@ -44,7 +44,7 @@ is used.
 
 Options:
 
-  -h              Print this help.
+  -h, --help      Print this help.
 
   -o <filename>   Set the output filename. Use '-' to mean stdout.
   --version       Display assembler version information.
@@ -92,6 +92,10 @@ int main(int argc, char** argv) {
                    SPV_SPIRV_VERSION_MINOR, SPV_SPIRV_VERSION_REVISION);
             return 0;
           }
+          if (0 == strcmp(argv[argi], "--help")) {
+            print_usage(argv[0]);
+            return 0;
+          }
         } break;
         default:
           print_usage(argv[0]);

tools/val/val.cpp

@@ -44,7 +44,8 @@ or if the filename is "-", then the binary is read from standard input.
 NOTE: The validator is a work in progress.
 
 Options:
-  --version  Display validator version information
+  -h, --help   Print this help.
+  --version    Display validator version information.
 )",
       argv0, argv0);
 }
@@ -64,6 +65,9 @@ int main(int argc, char** argv) {
         printf("Target: SPIR-V %d.%d rev %d\n", SPV_SPIRV_VERSION_MAJOR,
                SPV_SPIRV_VERSION_MINOR, SPV_SPIRV_VERSION_REVISION);
         return 0;
+      } else if (0 == strcmp(cur_arg, "--help") || 0 == strcmp(cur_arg, "-h")) {
+        print_usage(argv[0]);
+        return 0;
       } else if (0 == cur_arg[1]) {
         // Setting a filename of "-" to indicate stdin.
         if (!inFile) {