[C++20] [Modules] Allow to compile a pcm with and without -fPIC

seperately

We can compile a module unit in 2 phase compilaton:

```
clang++ -std=c++20 a.cppm --precompile -o a.pcm
clang++ -std=c++20 a.pcm -c -o a.o
```

And it is a general requirement that we need to compile a translation
unit with and without -fPIC for static and shared libraries.

But for C++20 modules with 2 phase compilation, it may be waste of time
to compile them 2 times completely. It may be fine to generate one BMI
and compile it with and without -fPIC seperately.

e.g.,

```
clang++ -std=c++20 a.cppm --precompile -o a.pcm
clang++ -std=c++20 a.pcm -c -o a.o
clang++ -std=c++20 a.pcm -c -fPIC -o a-PIC.o
```

Then we can save the time to parse a.cppm repeatedly.

1 files changed, 1 insertions, 1 deletions

diff --git a/clang/lib/Frontend/FrontendAction.cpp b/clang/lib/Frontend/FrontendAction.cpp
index eff785b..b9fd9b8 100644
--- a/clang/lib/Frontend/FrontendAction.cpp
+++ b/clang/lib/Frontend/FrontendAction.cpp
@@ -689,7 +689,7 @@ bool FrontendAction::BeginSourceFile(CompilerInstance &CI,
     std::unique_ptr<ASTUnit> AST = ASTUnit::LoadFromASTFile(
         std::string(InputFile), CI.getPCHContainerReader(),
         ASTUnit::LoadEverything, Diags, CI.getFileSystemOpts(),
-        CI.getHeaderSearchOptsPtr());
+        CI.getHeaderSearchOptsPtr(), CI.getLangOptsPtr());
 
     if (!AST)
       return false;