[clang] Initialize the file system explicitly (#158381)

This PR is a part of the effort to make the VFS used in the compiler
more explicit and consistent.

Instead of creating the VFS deep within the compiler (in
`CompilerInstance::createFileManager()`), clients are now required to
explicitly call `CompilerInstance::createVirtualFileSystem()` and
provide the base VFS from the outside.

This PR also helps in breaking up the dependency cycle where creating a
properly configured `DiagnosticsEngine` requires a properly configured
VFS, but creating properly configuring a VFS requires the
`DiagnosticsEngine`.

Both `CompilerInstance::create{FileManager,Diagnostics}()` now just use
the VFS already in `CompilerInstance` instead of taking one as a
parameter, making the VFS consistent across the instance sub-object.

1 files changed, 3 insertions, 1 deletions

diff --git a/lldb/source/Commands/CommandObjectTarget.cpp b/lldb/source/Commands/CommandObjectTarget.cpp
index 0f96fa9..940be42 100644
--- a/lldb/source/Commands/CommandObjectTarget.cpp
+++ b/lldb/source/Commands/CommandObjectTarget.cpp
@@ -2210,7 +2210,9 @@ protected:
 
     const char *clang_args[] = {"clang", pcm_path};
     clang::CompilerInstance compiler(clang::createInvocation(clang_args));
-    compiler.createDiagnostics(*FileSystem::Instance().GetVirtualFileSystem());
+    compiler.setVirtualFileSystem(
+        FileSystem::Instance().GetVirtualFileSystem());
+    compiler.createDiagnostics();
 
     // Pass empty deleter to not attempt to free memory that was allocated
     // outside of the current scope, possibly statically.