Swift: Turn of caching and integrated driver in autobuild

* Caching cases compiler invocations to be omitted. You can try this for
  yourself by turning on caching while building the project from the
  `xcode-hello` integration test, then cleaning of the build artifacts
  and building the project again while caching is enabled. This yields
  a database that is practically empty.
* The integrated driver causes compiler invocations to depend on modules
  shipped with Xcode. Those are unfortunately incompatible with our
  extractor.

Author: jketema

swift/swift-autobuilder/BuildRunner.cpp

@@ -79,6 +79,9 @@ bool buildXcodeTarget(const XcodeTarget& target, bool dryRun) {
   argv.push_back(target.name);
   argv.push_back("CODE_SIGNING_REQUIRED=NO");
   argv.push_back("CODE_SIGNING_ALLOWED=NO");
+  argv.push_back("COMPILATION_CACHE_ENABLE_CACHING=NO");
+  argv.push_back("SWIFT_ENABLE_COMPILE_CACHE=NO");
+  argv.push_back("SWIFT_USE_INTEGRATED_DRIVER=NO");
   return run_build_command(argv, dryRun);
 }