[preset] Add llvm-project pull request preset

Author: shahmishal

utils/build-presets.ini

@@ -1646,6 +1646,18 @@ sil-verify-all-macos-only
 skip-test-ios-host
 skip-test-watchos-host
 
+[preset: llvm_project_pull_request]
+mixin-preset=buildbot_all_platforms,tools=RA,stdlib=RA
+
+llvm-include-tests
+
+# Skip downstream project tests
+skip-test-watchos
+skip-test-swiftsyntax
+skip-test-indexstore-db
+skip-test-sourcekit-lsp
+skip-test-swiftpm
+skip-test-llbuild
 
 #===------------------------------------------------------------------------===#
 # Test watchOS on OS X builder