[clang] [llvm] [mlir] [CMake] Add dependent project mode for Flang's MLIR (PR #221724)

[Erich Keane via cfe-commits]

erichkeane wrote:

> > TBH, I was/am confused by that suggestion. I don't see really how it relates to a python-language or something wanting to speed up their MLIR build?
> 
> Users have always had the flexibility to selectively build dependencies, e.g. `ninja install-clang` will not build random unrelated LLVM tools but `ninja install` will. The onus is on the end user to make use of these if they need a smaller dependency tree, components are just an LLVM approved way to 'build your own distribution'. If a python language wanted to speed up their MLIR build, then MLIR just needs to provide sufficient targets for the end user.

Ok, thanks for that.  I'm definitely willing to admit that my 'vision' of the fix here was misguided.

https://github.com/llvm/llvm-project/pull/221724