Output a Windows-style response file for swift-frontend and clang

[ahoppen]

#1000 switched to use POSIX-style response files but swift-frontend expects Windows-style response files on Windows.

Switch back to generating Windows-style response files on Windows and pass --rsp-quoting=windows to clang to tell it to pass the response file in Windows mode.

Alternatives considered:

• Have a separate response file generation logic for clang and Swift: This seems like a continuous source of bugs if you always need to think about which response file format you want, especially if the behavior is not intuitive (clang.exe expecting POSIX-style response files)
• Instead of parsing --rsp-quoting=windows on Windows, use clang-cl.exe, which also causes response files to be parsed in Windows-style: I think it’s better to be explicit here instead of relying on clang’s implicit behavior based on which executable name was invoked.
• Change swift-frontend to accept POSIX-style response files: swift-frontend and the old Swift driver share the same response file parsing logic. Changing swift-frontend without changing the old driver would require a bunch of flag parsing, which isn’t desirable. Also, using Windows-style response files on Windows seems like the better-fitting solution (CMake, for example, outputs Windows-style response files).

Reverts #1000 with some logic added on top.

[ahoppen]

@swift-ci Please test

[ahoppen]

@swift-ci Please test macOS

[hjyamauchi]

@ahoppen It seems like we started to get this compile error in our internal app in the last few days with the tip of tree swift on windows:

LINK : warning LNK4044: unrecognized option '/-rsp-quoting=windows'; ignored LINK : warning LNK4044: unrecognized option '/LIB'; ignored LINK : fatal error LNK1104: cannot open file 'swiftSwiftOnoneSupport.lib' 

Though this may be a cmake issue, do you have thoughts? Does it look like the linker shouldn't get these options?

[ahoppen]

While I investigate a little more, do you use lld as a linker (ie. pass --use-lld) or any other linker? I assume the issue is that we should only pass -rsp-quoting=windows to clang.

[ahoppen]

#1717 should fix the issue. I assume you were building a static library without --use-lld, which used link.exe, which doesn’t support --rsp-quoting=windows.

[hjyamauchi]

@ahoppen Yeah probably we were using link.exe. I will try locally test the fix and update here. Thank you for looking into this!

[hjyamauchi]

@ahoppen I was able to confirm that #1717 fixes the issue. Thank you!

[ahoppen]

Thanks for verifying, @hjyamauchi!