Provide swift-frontend path when running integration tests

[cltnschlosser]

Fixes the issues I was running into: https://forums.swift.org/t/lots-of-errors-running-swift-driver-integration-tests/47986

Still 90 failing tests, which is more than the 50 from March 27: dadb0a3

A lot of Dependencies tests failing with similar looking errors, but first step is actually being able to run the tests :)
This is an example error snippet if anyone is curious:

            8: Failed to read dependency file
check:12'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
            9: Traceback (most recent call last):
check:12'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
           10:  File "SOURCE_DIR/test/Driver/Dependencies/Inputs/update-dependencies.py", line 53, in <module>
check:12'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
           11:  shutil.copyfile(primaryFile, depsFile)
check:12'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
           12:  File "/usr/local/Cellar/python@3.9/3.9.1_7/Frameworks/Python.framework/Versions/3.9/lib/python3.9/shutil.py", line 264, in copyfile
check:12'0     

[davidungar]

Aside from a thought about "python4" (!) it looks fine to me. Would be interested in what you think about that.

[cltnschlosser]

@swift-ci please test

[cltnschlosser]

Running a cross repo test run before merging, just to double check that I don't break anything.

Also figured out what was causing all those Driver/Dependencies failures. It was that I was running the tests in parallel. I'm down to 46 Failures total now, so that's good :)

Any ideas what might be causing the hiccups when running Driver/Dependencies tests in parallel with the other tests? Never had any issues in the past. Maybe some new shared dependencies file location? Is this expected? or a regression that needs to be investigated?

[cltnschlosser]

Any ideas what might be causing the hiccups when running Driver/Dependencies tests in parallel with the other tests? Never had any issues in the past. Maybe some new shared dependencies file location? Is this expected? or a regression that needs to be investigated?

Just realized the cause of the failures is rather obvious. These will both run test/Driver/Dependencies. If the same tests are running at the same time they will do things like delete the temporary directory that another instance of the same test was using.

  func testLitDriverTests() throws {
    guard ProcessEnv.vars.keys.contains("SWIFT_DRIVER_ENABLE_FAILING_INTEGRATION_TESTS") else {
      throw XCTSkip("Not all Driver tests supported")
    }
    try runLitTests(suite: "test", "Driver")
  }

  func testLitDriverDependenciesTests() throws {
    try runLitTests(suite: "test", "Driver", "Dependencies")
  }