[swiftpm] Add preset for SwiftPM Linux build

Intended for the Linux smoke test job that currently does not use a
preset.

Author: benlangmuir

utils/build-presets.ini

@@ -1386,6 +1386,33 @@ skip-test-swift
 skip-test-cmark
 skip-test-llbuild
 
+#===------------------------------------------------------------------------===#
+# Test swiftPM on Linux builder
+#===------------------------------------------------------------------------===#
+
+[preset: buildbot_swiftpm_linux_platform,tools=RA,stdlib=RA]
+mixin-preset=buildbot_incremental_base
+
+build-subdir=buildbot_incremental
+
+# Build Release without debug info, because it is faster to build.
+release
+assertions
+
+swiftpm
+
+xctest
+foundation
+libdispatch
+llbuild
+
+skip-test-swift
+skip-test-cmark
+skip-test-llbuild
+skip-test-libdispatch
+skip-test-foundation
+skip-test-xctest
+
 #===------------------------------------------------------------------------===#
 # Test llbuild on macOS builder
 #===------------------------------------------------------------------------===#