[clang][deps] Fix handling of -MT in module command-line

Follow-up to 6626f6fec3d3, this fixes the handling of -MT
* If no targets are provided, we need to invent one since cc1 expects
  the driver to have handled it. The default is to use -o, quoting as
  necessary for a make target.
* Fix the splitting for empty string, which was incorrectly treated as
  {""} instead of {}.
* Add a way to test this behaviour in clang-scan-deps.

Differential Revision: https://reviews.llvm.org/D129607

2 files changed, 36 insertions, 0 deletions

diff --git a/clang/lib/Basic/CMakeLists.txt b/clang/lib/Basic/CMakeLists.txt
index c815b57..89dd332 100644
--- a/clang/lib/Basic/CMakeLists.txt
+++ b/clang/lib/Basic/CMakeLists.txt
@@ -54,6 +54,7 @@ add_clang_library(clangBasic
   IdentifierTable.cpp
   LangOptions.cpp
   LangStandards.cpp
+  MakeSupport.cpp
   Module.cpp
   ObjCRuntime.cpp
   OpenCLOptions.cpp
diff --git a/clang/lib/Basic/MakeSupport.cpp b/clang/lib/Basic/MakeSupport.cpp
new file mode 100644
index 0000000..37838f7
--- /dev/null
+++ b/clang/lib/Basic/MakeSupport.cpp
@@ -0,0 +1,35 @@
+//===-- MakeSuport.cpp --------------------------------------------------*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/Basic/MakeSupport.h"
+
+void clang::quoteMakeTarget(StringRef Target, SmallVectorImpl<char> &Res) {
+  for (unsigned i = 0, e = Target.size(); i != e; ++i) {
+    switch (Target[i]) {
+    case ' ':
+    case '\t':
+      // Escape the preceding backslashes
+      for (int j = i - 1; j >= 0 && Target[j] == '\\'; --j)
+        Res.push_back('\\');
+
+      // Escape the space/tab
+      Res.push_back('\\');
+      break;
+    case '$':
+      Res.push_back('$');
+      break;
+    case '#':
+      Res.push_back('\\');
+      break;
+    default:
+      break;
+    }
+
+    Res.push_back(Target[i]);
+  }
+}
\ No newline at end of file