[Clang][Tooling] Accept preprocessed input files

This restores the tooling library's ability to accept invocations that take a
preprocessed file as the primary input.

Regressed by https://reviews.llvm.org/D105695
Fixes #63941

Differential Revision: https://reviews.llvm.org/D157011

clang/lib/Tooling/Tooling.cpp

@@ -147,6 +147,13 @@ getCC1Arguments(DiagnosticsEngine *Diagnostics,
     if (IsCC1Command(Job) && llvm::all_of(Job.getInputInfos(), IsSrcFile))
       CC1Jobs.push_back(&Job);
 
+  // If there are no jobs for source files, try checking again for a single job
+  // with any file type. This accepts a preprocessed file as input.
+  if (CC1Jobs.empty())
+    for (const driver::Command &Job : Jobs)
+      if (IsCC1Command(Job))
+        CC1Jobs.push_back(&Job);
+
   if (CC1Jobs.empty() ||
       (CC1Jobs.size() > 1 && !ignoreExtraCC1Commands(Compilation))) {
     SmallString<256> error_msg;

clang/unittests/Tooling/ToolingTest.cpp

@@ -449,6 +449,13 @@ TEST_F(CommandLineExtractorTest, AcceptSaveTemps) {
   EXPECT_NE(extractCC1Arguments(Args), nullptr);
 }
 
+TEST_F(CommandLineExtractorTest, AcceptPreprocessedInputFile) {
+  addFile("test.i", "int main() {}\n");
+  const char *Args[] = {"clang", "-target", "arm64-apple-macosx11.0.0", "-c",
+                        "test.i"};
+  EXPECT_NE(extractCC1Arguments(Args), nullptr);
+}
+
 TEST_F(CommandLineExtractorTest, RejectMultipleArchitectures) {
   addFile("test.c", "int main() {}\n");
   const char *Args[] = {"clang", "-target", "arm64-apple-macosx11.0.0",