[clang] [Preprocessor] Do not expand macros if the input is already preprocessed (PR #137665)

[Juan Manuel Martinez Caamaño via cfe-commits]

================
@@ -1558,6 +1558,7 @@ void clang::InitializePreprocessor(Preprocessor &PP,
                                    const PCHContainerReader &PCHContainerRdr,
                                    const FrontendOptions &FEOpts,
                                    const CodeGenOptions &CodeGenOpts) {
+
----------------
jmmartinez wrote:

This slipped in, remove this change.

https://github.com/llvm/llvm-project/pull/137665