Index: lib/Frontend/CompilerInstance.cpp
===================================================================
--- lib/Frontend/CompilerInstance.cpp
+++ lib/Frontend/CompilerInstance.cpp
@@ -759,9 +759,15 @@
 
   if (UseTemporary) {
     // Create a temporary file.
-    SmallString<128> TempPath;
-    TempPath = OutFile;
+    // Insert -%%%%%%%% before the extension (if any), and because some tools
+    // (noticeable, clang's own GlobalModuleIndex.cpp) glob for build
+    // artifacts, also append .tmp.
+    StringRef OutputExtension = llvm::sys::path::extension(OutFile);
+    SmallString<128> TempPath =
+        StringRef(OutFile).drop_back(OutputExtension.size());
     TempPath += "-%%%%%%%%";
+    TempPath += OutputExtension;
+    TempPath += ".tmp";
     int fd;
     std::error_code EC =
         llvm::sys::fs::createUniqueFile(TempPath, fd, TempPath);