[clang] [CMake][Release] Build with -ffat-lto-objects (PR #140381)

[Tobias Hieta via cfe-commits]

tru wrote:

> > How much slower is this? Last time I tested fatlto in our toolchain it took a VERY long time to link.
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> 
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> You're probably thinking about "full" LTO, this is fat thin LTO. Our naming is truly amazing. See https://llvm.org/docs/FatLTO.html.
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> 
> 
> It should add about 10% overhead.

Oh great. In that case this seems fine!

https://github.com/llvm/llvm-project/pull/140381