swift

61050770 - build-script: validate arguments before running `sccache` (#61375)

build-script: validate arguments before running `sccache` (#61375) When a user passes `--sccache` flag when `sccache` is not installed, we still attempt to make a shell invocation to `sccache`, which leads to an inscrutable error: ``` Traceback (most recent call last): File "/root/swift-source/swift/utils/build-script", line 789, in <module> exit_code = main() File "/root/swift-source/swift/utils/build-script", line 784, in main return main_normal() File "/root/swift-source/swift/utils/build-script", line 687, in main_normal shell.capture([toolchain.sccache, "--show-stats"]) File "/root/swift-source/swift/utils/swift_build_support/swift_build_support/shell.py", line 133, in capture return subprocess.check_output(command, env=_env, stderr=stderr, File "/usr/lib/python3.10/subprocess.py", line 420, in check_output return run(*popenargs, stdout=PIPE, timeout=timeout, check=True, File "/usr/lib/python3.10/subprocess.py", line 501, in run with Popen(*popenargs, **kwargs) as process: File "/usr/lib/python3.10/subprocess.py", line 969, in __init__ self._execute_child(args, executable, preexec_fn, close_fds, File "/usr/lib/python3.10/subprocess.py", line 1720, in _execute_child and os.path.dirname(executable) File "/usr/lib/python3.10/posixpath.py", line 152, in dirname p = os.fspath(p) TypeError: expected str, bytes or os.PathLike object, not NoneType ``` `validate_arguments` should be called before `shell.capture([toolchain.sccache, "--show-stats"])` so that a more meaningful error message is shown to the user, asking them to install `sccache`.