Make swift driver friendlier to relative paths

[zienag]

Add handling for relative paths in output file map path,
resonse file paths, recorded input modification dates.

[owenv]

LGTM, this looks like it should make path management a lot more consistent!

[owenv]

@swift-ci test

[owenv]

@zienag sorry for taking so long to come back to this. It looks one of the response file tests is failing on CI

[zienag]

@zienag sorry for taking so long to come back to this. It looks one of the response file tests is failing on CI

Hmm, that is unfortunately non trivial bug: given arguments

swiftc -Xlinker @SOMETHING

expandResponseFiles would think that @SOMETHING is response file passed to driver. Before my changes it tried to make absolute path from SOMETHING, failed and skipped that argument. Now it makes relative path from SOMETHING and tries to read its content. This behaviour is totally wrong, and likely deserves separate pr.

Do you know any code/place that works with -Xblabla arg arguments to ignore or filter them out in expandResponseFiles?

[zienag]

Meanwhile, I'll remove changes associated with response file from this pr, as extensions I've added are needed by other prs

[cltnschlosser]

Unfortunate that you had to undo some of the work for response files, but this looks good!

[owenv]

@zienag unfortunately I don't have a good idea about how to handle -X... arguments with response files. This might cause problems when we eventually migrate to swift-argument-parser too. In the meantime, the rest of this change will still be really helpful though!

[owenv]

@swift-ci test

[owenv]

@swift-ci test

[owenv]

Looks like the checks are all passing now. Thanks @zienag !