Add --pkg-config-path to LocationOptions

[MaxDesiatov]

Resolves #5815.

Motivation:

--pkg-config-path option is less fragile and easier to report errors on than PKG_CONFIG_PATH environment variable.

Modifications:

Added pkgConfigDirectory to LocationOptions, which is propagated to BuildPlan as a function or initializer argument.

Result:

--pkg-config-path is available as a command-line option.

[neonichu]

I believe PKG_CONFIG_PATH is a list of paths, so if we want to provide an alternative to it, we should probably also take a list here.

If I read this correctly, it is also not being passed to XCBuild support, yet, we should do that.

[MaxDesiatov]

I believe PKG_CONFIG_PATH is a list of paths, so if we want to provide an alternative to it, we should probably also take a list here.

Would it make sense to make them comma-separated? I wonder if just changing the type on the option declaration to [AbsolutePath] would work with some built-in support from ArgumentParser?

If I read this correctly, it is also not being passed to XCBuild support, yet, we should do that.

Is there anything to adjust other than this place in PIFBuilder.swift? https://github.com/apple/swift-package-manager/pull/5949/files#diff-4558ab2f4d59c923d54773a355350f9362890d5b982aaf79ae5854f8e93eb09fR703

[neonichu]

Would it make sense to make them comma-separated? I wonder if just changing the type on the option declaration to [AbsolutePath] would work with some built-in support from ArgumentParser?

Not sure, but we should do whatever is the most canonical way to do this. Maybe @natecook1000 has hints

[MaxDesiatov]

@swift-ci please smoke test

[MaxDesiatov]

@swift-ci please smoke test

[MaxDesiatov]

@swift-ci smoke test

[MaxDesiatov]

Would it make sense to make them comma-separated? I wonder if just changing the type on the option declaration to [AbsolutePath] would work with some built-in support from ArgumentParser?

Not sure, but we should do whatever is the most canonical way to do this.

@neonichu turns out, specifying it as [AbsolutePath] allows passing the option multiple times. I've also added tests and updated CHANGELOG.md, this is now ready for review.

[MaxDesiatov]

@swift-ci smoke test

[MaxDesiatov]

@swift-ci smoke test

[finagolfin]

I was hoping we'd get this in before the 5.8 branch tomorrow, still possible?

[MaxDesiatov]

I'm not sure, it depends on whether anyone is available for a review.

[MaxDesiatov]

@swift-ci smoke test

[tomerd]

I think we should sort these

[MaxDesiatov]

It's already in reverse chronological order, or would you like to see some other sorting?

[tomerd]

I think the rest of the document has is non-reverse chronological order?

[finagolfin]

I can confirm that this flag works when cross-compiling SPM for Android with the latest 5.8 Dec. 20 snapshot, thanks.