[clang] [llvm] [CMAKE] Enable FatLTO as a build option for LLVM (PR #80480)

[Petr Hosek via cfe-commits]

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@@ -1251,6 +1253,10 @@ elseif(LLVM_ENABLE_LTO)
   endif()
 endif()
 
+if(LLVM_ENABLE_FATLTO AND (FUCHSIA OR UNIX))
+    append("-ffat-lto-objects" CMAKE_EXE_LINKER_FLAGS CMAKE_SHARED_LINKER_FLAGS)
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petrhosek wrote:

I'd also include the flag in `CMAKE_MODULE_LINKER_FLAGS` for completeness.

https://github.com/llvm/llvm-project/pull/80480