run_single_test: add a --quick option to skip compiler/tool checking

This can be the longest part of the entire test process, often with no
benefit because we already know the environment is sane. So, let's have
an option save some time.

run_single_test.py

@@ -27,6 +27,7 @@ if T.TYPE_CHECKING:
         subtests: T.List[int]
         backend: str
         extra_args: T.List[str]
+        quick: bool
 
 
 def main() -> None:
@@ -39,9 +40,11 @@ def main() -> None:
     parser.add_argument('--cross-file', action='store', help='File describing cross compilation environment.')
     parser.add_argument('--native-file', action='store', help='File describing native compilation environment.')
     parser.add_argument('--use-tmpdir', action='store_true', help='Use tmp directory for temporary files.')
+    parser.add_argument('--quick', action='store_true', help='Skip some compiler and tool checking')
     args = T.cast('ArgumentType', parser.parse_args())
 
     setup_commands(args.backend)
+    if not args.quick:
         detect_system_compiler(args)
         print_tool_versions()