Merge pull request #17753 from rintaro/sourcekit-rdar40646921-2

 [SourceKit] Use "-" as fallback complier argument

Author: rintaro

test/SourceKit/DocumentStructure/structure.swift

@@ -6,3 +6,9 @@
 
 // RUN: %sourcekitd-test -req=structure %S/../Inputs/placeholders.swift | %sed_clean > %t.placeholders.response
 // RUN: diff -u %s.placeholders.response %t.placeholders.response
+
+// RUN: %sourcekitd-test -req=structure %S/Inputs/main.swift -name -foobar | %sed_clean > %t.foobar.response
+// RUN: diff -u %s.foobar.response %t.foobar.response
+
+// RUN: %sourcekitd-test -req=structure -text-input %S/Inputs/main.swift | %sed_clean > %t.empty.response
+// RUN: diff -u %s.empty.response %t.empty.response