build libdispatch by default in both linux build bot configurations

Author: phausler

utils/build-presets.ini

@@ -646,11 +646,13 @@ test
 validation-test
 long-test
 foundation
+libdispatch
 lit-args=-v
 
 dash-dash
 
 install-foundation
+install-libdispatch
 reconfigure
 
 # Ubuntu 16.04 preset for backwards compat and future customizations.
@@ -722,6 +724,7 @@ llbuild
 swiftpm
 xctest
 foundation
+libdispatch
 dash-dash
 
 [preset: buildbot_incremental_linux,long_test]