[Index] Update tests to expect only indexing of SDK modules

Author: xymus

test/Index/Store/cross-import-overlay.swift

@@ -3,7 +3,7 @@
 // RUN: cp -r %S/../Inputs/CrossImport %t/CrossImport
 // RUN: %{python} %S/../../CrossImport/Inputs/rewrite-module-triples.py %t/CrossImport %module-target-triple
 
-// RUN: %target-swift-frontend -disable-implicit-concurrency-module-import -disable-implicit-string-processing-module-import -c -index-store-path %t/idx -module-cache-path %t/mcp -index-system-modules -index-ignore-stdlib -enable-cross-import-overlays %s -Fsystem %t/CrossImport -o %t/file1.o -module-name cross_import_overlay
+// RUN: %target-swift-frontend -disable-implicit-concurrency-module-import -disable-implicit-string-processing-module-import -c -index-store-path %t/idx -module-cache-path %t/mcp -index-system-modules -index-ignore-stdlib -enable-cross-import-overlays %s -Fsystem %t/CrossImport -o %t/file1.o -module-name cross_import_overlay -sdk %t
 // RUN: c-index-test core -print-unit %t/idx > %t/units
 
 import A