Fix build break.

Author: qiongsiwu

clang/lib/Tooling/DependencyScanning/DependencyScannerImpl.cpp

@@ -717,7 +717,7 @@ llvm::Error CompilerInstanceWithContext::initialize() {
       CommandLine, OverlayFS, DiagPrinterWithOS->DiagPrinter);
 
   std::tie(Driver, Compilation) = buildCompilation(
-      CommandLine, *DiagEngineWithCmdAndOpts->DiagEngine, OverlayFS);
+      CommandLine, *DiagEngineWithCmdAndOpts->DiagEngine, OverlayFS, Alloc);
 
   if (!Compilation) {
     return llvm::make_error<llvm::StringError>("Failed to build compilation",

clang/lib/Tooling/DependencyScanning/DependencyScannerImpl.h

@@ -168,6 +168,9 @@ class CompilerInstanceWithContext {
   std::unique_ptr<DignosticsEngineWithDiagOpts> DiagEngineWithCmdAndOpts;
 
   // Context - compiler invocation
+  // Compilation's command's arguments may be owned by Alloc when expanded from
+  // response files, so we need to keep Alloc alive in the context.
+  llvm::BumpPtrAllocator Alloc;
   std::unique_ptr<clang::driver::Driver> Driver;
   std::unique_ptr<clang::driver::Compilation> Compilation;
   std::unique_ptr<CompilerInvocation> OriginalInvocation;