Fix ld warning

[ianpartridge]

When building the SwiftXCTest target in Xcode 9 beta 4, ld reports the following warning:

Ld /Users/ipartrid/Library/Developer/Xcode/DerivedData/Foundation-dlbuoxyagtlausbjtyopapynebeb/Build/Products/Debug/SwiftXCTest.framework/Versions/A/SwiftXCTest normal x86_64
    cd /Users/ipartrid/swift-corelibs-xctest
    export MACOSX_DEPLOYMENT_TARGET=10.11
    /Applications/Xcode-beta.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang -arch x86_64 -dynamiclib -isysroot /Applications/Xcode-beta.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.13.sdk -L/Users/ipartrid/Library/Developer/Xcode/DerivedData/Foundation-dlbuoxyagtlausbjtyopapynebeb/Build/Products/Debug -F/Users/ipartrid/Library/Developer/Xcode/DerivedData/Foundation-dlbuoxyagtlausbjtyopapynebeb/Build/Products/Debug -F../swift-corelibs-foundation/build/Debug -filelist /Users/ipartrid/Library/Developer/Xcode/DerivedData/Foundation-dlbuoxyagtlausbjtyopapynebeb/Build/Intermediates.noindex/XCTest.build/Debug/SwiftXCTest.build/Objects-normal/x86_64/SwiftXCTest.LinkFileList -install_name @rpath/SwiftXCTest.framework/Versions/A/SwiftXCTest -Xlinker -rpath -Xlinker @executable_path/../Frameworks -Xlinker -rpath -Xlinker @loader_path/Frameworks -mmacosx-version-min=10.11 -Xlinker -object_path_lto -Xlinker /Users/ipartrid/Library/Developer/Xcode/DerivedData/Foundation-dlbuoxyagtlausbjtyopapynebeb/Build/Intermediates.noindex/XCTest.build/Debug/SwiftXCTest.build/Objects-normal/x86_64/SwiftXCTest_lto.o -Xlinker -export_dynamic -Xlinker -no_deduplicate -fobjc-link-runtime -L/Applications/Xcode-beta.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/swift/macosx -Xlinker -add_ast_path -Xlinker /Users/ipartrid/Library/Developer/Xcode/DerivedData/Foundation-dlbuoxyagtlausbjtyopapynebeb/Build/Intermediates.noindex/XCTest.build/Debug/SwiftXCTest.build/Objects-normal/x86_64/SwiftXCTest.swiftmodule -framework SwiftFoundation -single_module -Xlinker -dependency_info -Xlinker /Users/ipartrid/Library/Developer/Xcode/DerivedData/Foundation-dlbuoxyagtlausbjtyopapynebeb/Build/Intermediates.noindex/XCTest.build/Debug/SwiftXCTest.build/Objects-normal/x86_64/SwiftXCTest_dependency_info.dat -o /Users/ipartrid/Library/Developer/Xcode/DerivedData/Foundation-dlbuoxyagtlausbjtyopapynebeb/Build/Products/Debug/SwiftXCTest.framework/Versions/A/SwiftXCTest

ld: warning: directory not found for option '-F../swift-corelibs-foundation/build/Debug'

As far as I can tell, this directory is just not used by the build system and I'm not sure why it's been added to the Framework Search Paths for that target.

This PR removes the references, and hence the warning.

[modocache]

@swift-ci please test

[modocache]

It looks like this was intentionally added in #192. Maybe @spevans would have a better idea whether it's still necessary?

[ianpartridge]

Ah, thanks I hadn't found #192. Maybe this PR is wrong then.

[spevans]

I think as long as you can open XCTest.xcworkspace and run the test on TestFoundation ok then this is fine. Also the same for Foundation.workspace for swiftlang/swift-corelibs-foundation#1139 (which worked ok for me)

[spevans]

Btw, I think the tests for the XCTest PRs actually build using Xcode on the CI server so if the Swift Test OSX Platform comes back ok then I think we are good. Although I think it does a Debug build of swift hence why it seems to take 2.5 hours!

[ianpartridge]

Thanks @spevans hopefully we are good with this one then.

[briancroom]

I could imagine the projects building to that directory if you opened the xcodeproj directly and had Xcode configured to use a custom build directory. Nonetheless with the workspace and the usual configuration, Foundation and XCTest should build to the shared DerivedData without extra search paths being needed.

The CI checks passed, so I think we're good. Thanks @ianpartridge!