[clang] [clang][lex] Use `FileManager` to make prebuilt module paths absolute (PR #165347)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Jan Svoboda (jansvoboda11)

<details>
<summary>Changes</summary>

This PR switches from using `llvm::sys::fs::make_absolute()` to `FileManager::makeAbsolutePath()` so that `FileSystemOptions` (i.e. the `-working-directory` option) and the `VFS`'s CWD have a say in how the prebuilt module paths are resolved. This matches how the rest of the compiler treats input files.

---
Full diff: https://github.com/llvm/llvm-project/pull/165347.diff


1 Files Affected:

- (modified) clang/lib/Lex/HeaderSearch.cpp (+2-2) 


``````````diff
diff --git a/clang/lib/Lex/HeaderSearch.cpp b/clang/lib/Lex/HeaderSearch.cpp
index 65c324c10ca5d..f05c28fd7a123 100644
--- a/clang/lib/Lex/HeaderSearch.cpp
+++ b/clang/lib/Lex/HeaderSearch.cpp
@@ -221,7 +221,7 @@ std::string HeaderSearch::getPrebuiltModuleFileName(StringRef ModuleName,
   // file.
   for (const std::string &Dir : HSOpts.PrebuiltModulePaths) {
     SmallString<256> Result(Dir);
-    llvm::sys::fs::make_absolute(Result);
+    FileMgr.makeAbsolutePath(Result);
     if (ModuleName.contains(':'))
       // The separator of C++20 modules partitions (':') is not good for file
       // systems, here clang and gcc choose '-' by default since it is not a
@@ -246,7 +246,7 @@ std::string HeaderSearch::getPrebuiltImplicitModuleFileName(Module *Module) {
   StringRef ModuleCacheHash = HSOpts.DisableModuleHash ? "" : getModuleHash();
   for (const std::string &Dir : HSOpts.PrebuiltModulePaths) {
     SmallString<256> CachePath(Dir);
-    llvm::sys::fs::make_absolute(CachePath);
+    FileMgr.makeAbsolutePath(CachePath);
     llvm::sys::path::append(CachePath, ModuleCacheHash);
     std::string FileName =
         getCachedModuleFileNameImpl(ModuleName, ModuleMapPath, CachePath);

``````````

</details>


https://github.com/llvm/llvm-project/pull/165347