[CAS] Don't leak -iapinotes-modules clang flag in caching build

The search paths for apinotes are leaked when using compilation caching
but they are not needed like other search path because the apinotes are
found and stored inside include-tree.

rdar://164205657

Author: cachemeifyoucan

lib/ClangImporter/ClangImporter.cpp

@@ -4363,6 +4363,9 @@ ClangImporter::getSwiftExplicitModuleDirectCC1Args() const {
   FEOpts.IncludeTimestamps = false;
   FEOpts.ModuleMapFiles.clear();
 
+  // APINotesOptions.
+  instance.getAPINotesOpts().ModuleSearchPaths.clear();
+
   // IndexStorePath is forwarded from swift.
   FEOpts.IndexStorePath.clear();
 

test/CAS/apinotes.swift

@@ -0,0 +1,29 @@
+// REQUIRES: objc_interop
+
+// RUN: %empty-directory(%t)
+// RUN: split-file %s %t
+
+// RUN: %target-swift-frontend -scan-dependencies -module-name Test -module-cache-path %t/clang-module-cache -O \
+// RUN:   -disable-implicit-string-processing-module-import -disable-implicit-concurrency-module-import \
+// RUN:   %t/main.swift -o %t/deps.json -swift-version 5 -cache-compile-job -cas-path %t/cas -I %t
+
+// RUN: %FileCheck --input-file=%t/deps.json %s
+
+// CHECK-NOT: -iapinotes-modules
+
+//--- main.swift
+import A
+
+//--- module.modulemap
+module A { header "A.h" export *}
+
+//--- A.h
+#pragma once
+void a(void);
+
+//--- A.apinotes
+Name: A
+Functions:
+  - Name: a
+    Availability: none
+    AvailabilityMsg: "don't use this"