[build-script] Add preset for SwiftSyntax PR testing

Author: ahoppen

utils/build-presets.ini

@@ -1537,6 +1537,17 @@ assertions
 # Downstream projects that import llbuild+SwiftPM.
 sourcekit-lsp
 
+#===------------------------------------------------------------------------===#
+# Test Swift Syntax
+#===------------------------------------------------------------------------===#
+
+[preset: buildbot_swiftsyntax_macos]
+mixin-preset=mixin_swiftpm_package_macos_platform
+release
+assertions
+swiftsyntax
+swiftsyntax-verify-generated-files
+
 #===------------------------------------------------------------------------===#
 # Test Swift Stress Tester
 #===------------------------------------------------------------------------===#