[clang] [clang][InstallAPI] Introduce basic driver to write out tbd files (PR #81571)

[Juergen Ributzka via cfe-commits]

================
@@ -45,6 +45,7 @@
     ".rs",
     ".ifs",
     ".rc",
+    ".tbd",
----------------
ributzka wrote:

This doesn't seem to be used by the current tests.

https://github.com/llvm/llvm-project/pull/81571