[clang] [C++20] [Modules] Offer -fmodules-embed-all-files option (PR #107194)

[Chuanqi Xu via cfe-commits]

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@@ -462,6 +462,33 @@ Currently, Clang accepts the above example, though it may produce surprising
 results if the debugging code depends on consistent use of ``NDEBUG`` in other
 translation units.
 
+Source Files Consistency
+^^^^^^^^^^^^^^^^^^^^^^^^
+
+Clang may open the input files (*) of a BMI during the compilation. It implies that
+when we consume a BMI, all the input files need to be present with the same path
+and the same contents.
+
+To overcome the requirements and simplify cases like distributed builds and sandboxed
+builds, users can use ``-fmodules-embed-all-files`` flag to embed all input files
+into the BMI so that clang won't ask to open the corresponding file on disk.
+
+Input files (*): The source files that took part in the compilation of the BMI.
+For example,
----------------
ChuanqiXu9 wrote:

Done

https://github.com/llvm/llvm-project/pull/107194