[clang][modules] Strip LLVM options

Currently, the dep scanner does not remove LLVM options from the argument list.
Since LLVM options shouldn't affect the AST, it is safe to remove them all.

clang/lib/Tooling/DependencyScanning/ModuleDepCollector.cpp

@@ -119,6 +119,8 @@ makeCommonInvocationForModuleBuild(CompilerInvocation CI) {
   // units.
   CI.getFrontendOpts().Inputs.clear();
   CI.getFrontendOpts().OutputFile.clear();
+  // LLVM options are not going to affect the AST
+  CI.getFrontendOpts().LLVMArgs.clear();
 
   // TODO: Figure out better way to set options to their default value.
   CI.getCodeGenOpts().MainFileName.clear();

clang/test/ClangScanDeps/strip-llvm-args.m

@@ -0,0 +1,46 @@
+// RUN: rm -rf %t
+// RUN: split-file %s %t
+// RUN: sed -e "s|DIR|%/t|g" %t/cdb1.json.template > %t/cdb1.json
+
+// RUN: clang-scan-deps -compilation-database %t/cdb1.json -format experimental-full > %t/result1.txt
+// RUN: FileCheck %s -input-file %t/result1.txt
+
+// CHECK:        "modules": [
+// CHECK-NEXT:     {
+// CHECK:            "command-line": [
+// CHECK-NOT:          "-mllvm"
+// CHECK:            ]
+// CHECK:            "name": "A"
+// CHECK:          }
+// CHECK-NOT:        "name": "A"
+// CHECK:        "translation-units"
+
+//--- cdb1.json.template
+[
+  {
+    "directory": "DIR",
+    "command": "clang -Imodules/A -fmodules -fmodules-cache-path=DIR/module-cache -fimplicit-modules -fimplicit-module-maps -fsyntax-only DIR/t1.m",
+    "file": "DIR/t1.m"
+  },
+  {
+    "directory": "DIR",
+    "command": "clang -Imodules/A -fmodules -fmodules-cache-path=DIR/module-cache -fimplicit-modules -fimplicit-module-maps -mllvm -stackmap-version=2 -fsyntax-only DIR/t2.m",
+    "file": "DIR/t2.m"
+  }
+]
+
+//--- modules/A/module.modulemap
+
+module A {
+  umbrella header "A.h"
+}
+
+//--- modules/A/A.h
+
+typedef int A_t;
+
+//--- t1.m
+@import A;
+
+//--- t2.m
+@import A;