[clang] [clang][deps] Load module map file from PCM (PR #66389)

[Ben Langmuir via cfe-commits]

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@@ -1307,6 +1307,9 @@ void ModuleMap::setInferredModuleAllowedBy(Module *M,
 
 std::error_code
 ModuleMap::canonicalizeModuleMapPath(SmallVectorImpl<char> &Path) {
+  FileManager &FM = SourceMgr.getFileManager();
+  FM.makeAbsolutePath(Path);
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benlangmuir wrote:

This would also impact explicit module invocations.  I didn't realize the impact on path hash; good point that also seems like a concern.  I didn't consider ASTWriter would make it relative, so at least that case wouldn't be an issue.

https://github.com/llvm/llvm-project/pull/66389