sourcekitd/test: add an interface grouping test for user module.

Author: nkcsgexi

test/SourceKit/InterfaceGen/Inputs/group.json

@@ -0,0 +1,8 @@
+{
+  "A": [
+    "swift_mod.swift",
+  ],
+  "B": [
+    "swift_mod_syn.swift",
+  ]
+}

test/SourceKit/InterfaceGen/gen_module_group.swift

@@ -0,0 +1,12 @@
+// RUN: %empty-directory(%t.mod)
+// RUN: %target-swift-frontend -module-name MyModule -emit-module -emit-module-path %t.mod/MyModule.swiftmodule  -emit-module-doc -emit-module-doc-path %t.mod/MyModule.swiftdoc -group-info-path %S/Inputs/group.json %S/Inputs/swift_mod.swift %S/Inputs/swift_mod_syn.swift
+// RUN: %sourcekitd-test -req=interface-gen -module MyModule -group-name A -- -I %t.mod | %FileCheck -check-prefix=GROUPA %s
+// RUN: %sourcekitd-test -req=interface-gen -module MyModule -group-name B -- -I %t.mod | %FileCheck -check-prefix=GROUPB %s
+
+// GROUPA: MyClass
+// GROUPA-NOT: P1
+// GROUPA-NOT: P2
+
+// GROUPB: P1
+// GROUPB: P2
+// GROUPB-NOT: MyClass