Rollup merge of #126985 - Mrmaxmeier:dwarf-embed-source, r=davidtwco

Implement `-Z embed-source` (DWARFv5 source code embedding extension)

Implement https://github.com/rust-lang/compiler-team/issues/764 MCP which adds an unstable flag that exposes LLVM's [DWARFv5 source code embedding](https://dwarfstd.org/issues/180201.1.html) support.

compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -1860,6 +1860,8 @@ extern "C" {
         CSKind: ChecksumKind,
         Checksum: *const c_char,
         ChecksumLen: size_t,
+        Source: *const c_char,
+        SourceLen: size_t,
     ) -> &'a DIFile;
 
     pub fn LLVMRustDIBuilderCreateSubroutineType<'a>(