[build-script] Add a LLDB PR testing preset

Author: JDevlieghere

utils/build-presets.ini

@@ -296,6 +296,18 @@ lldb-build-type=Release
 lldb-test-swift-only
 lldb-assertions
 
+[preset: lldb-pull-request]
+lldb
+lldb-no-debugserver
+lldb-use-system-debugserver
+release-debuginfo
+test
+no-swift-stdlib-assertions
+skip-build-benchmarks
+skip-test-swift
+skip-test-cmark
+skip-early-swift-driver
+
 #===------------------------------------------------------------------------===#
 # Incremental buildbots for Darwin OSes
 #===------------------------------------------------------------------------===#