[Tests] Fix another early termination in tests

When running swift-driver test suite with an older compiler that doesn't support bridging header chaining, the second part of the bridging header caching test will just be a single job, from which the default executor will run the swift-frontend in-place. This will cause the test suite to early exit regardless of the state of the test suite.

Author: cachemeifyoucan

Tests/SwiftDriverTests/CachingBuildTests.swift

@@ -720,13 +720,13 @@ final class CachingBuildTests: XCTestCase {
  interModuleDependencyOracle: dependencyOracle)
  let jobs = try driver.planBuild()
  for job in jobs {
-  XCTAssertFalse(job.outputCacheKeys.isEmpty)
+ XCTAssertFalse(job.outputCacheKeys.isEmpty)
  }
- if driver.isFrontendArgSupported(.importPch) {
- XCTAssertTrue(jobs.contains { $0.kind == .generatePCH })
+ if driver.isFrontendArgSupported(.autoBridgingHeaderChaining) {
+ XCTAssertTrue(jobs.contains { $0.kind == .generatePCH })
+ try driver.run(jobs: jobs)
+ XCTAssertFalse(driver.diagnosticEngine.hasErrors)
  }
- try driver.run(jobs: jobs)
- XCTAssertFalse(driver.diagnosticEngine.hasErrors)
  }
  }