Use relative_path for local Swift packages

[jsorge]

PR #911 added support for local packages but did not add support for the relativePath property inside of the local package definition. Here's a sample from my pbxproj file:

/* Begin XCLocalSwiftPackageReference section */
		93ED17092AAED02600B3DB25 /* XCLocalSwiftPackageReference "../../Packages/SharedResources" */ = {
			isa = XCLocalSwiftPackageReference;
			relativePath = ../../Packages/SharedResources;
		};

When I try to use the new local package model I got the following error: [!] Xcodeproj doesn't know about the following attributes {"relativePath"=>"../../Packages/SharedResources"} for the 'XCLocalSwiftPackageReference' isa. and I believe that was because the class was looking for path (which doesn't exist) and not relativePath which does.

This PR fixes that problem for local packages.

[dnkoutso]

@jsorge can you have both path and relativePath? Why is the first one replaced?

[jsorge]

@jsorge can you have both path and relativePath? Why is the first one replaced?

I replaced it because I didn’t see path as a thing that could be parsed from the project file. Happy to add it back if it could be there.

[dnkoutso]

Wonder if an Xcode version upgrade replaced it or added it...................also wonder if there is harm in keeping both

[jsorge]

Added it back @dnkoutso

[serbancoroiu]

Fixed in the last release, works now. Thanks!