[build-script] For now make buildbot_incremental,tools=RA,stdlib=RA,xcode not test llbuild/swiftpm.

There are some issues related to llbuild/swiftpm building in Debug when the rest
of swift is Release. I have not looked into it yet and I would like to get this bot green.

I filed rdar://27061782.

Author: gottesmm

utils/build-presets.ini

@@ -264,6 +264,10 @@ skip-test-watchos
 stdlib-deployment-targets=macosx-x86_64
 swift-primary-variant-sdk=OSX
 swift-primary-variant-arch=x86_64
+skip-build-llbuild
+skip-test-llbuild
+skip-build-swiftpm
+skip-test-swiftpm
 
 # This preset is used by CI to test swift-corelibs-xctest.
 [preset: buildbot_incremental,tools=RA,stdlib=RA,XCTest]