XCUITests: uispecs, L10nSnapshots tests not running. Compilation error for those schemes

[isabelrios]

After this commit landed c268631 the build to launch the tests fails with this error:

###  ✗ <unknown>:0: error: invalid argument ‘-D-DDEBUG’; did you provide a redundant ‘-D’ in your build settings?
1409 Testing failed:
1410 Command CompileSwiftSources failed with a nonzero exit code
1411 Testing cancelled because the build failed.
1412
    ** TEST FAILED **
141 The following build commands failed:
1414 CompileSwiftSources normal x86_64 com.apple.xcode.tools.swift.compiler
    Test run failed!

The regular build and the unit tests work fine. Complete BB logs here

[isabelrios]

Hi @kaylagalway, wondering if you had time to check this issue. Tests are disabled and since there is activity and new PRs coming soon would be good to have them back running.