[clang] [compiler-rt] [llvm] Reapply "Skipping host target exports during cross-compilation" (#210… (PR #210496)

[Petr Hosek via cfe-commits]

================
@@ -313,6 +313,16 @@ macro(load_llvm_config)
       "You are not using the monorepo layout. This configuration is DEPRECATED.")
   endif()
 
+  # Exports from LLVM and Clang may contain shared libraries. When targeting
+  # baremetal platforms that lacks shared library support, importing such
+  # exports unrestrictedly will trigger cmake errors. Set
+  # LLVM_OMIT_EXPORTS_FROM_CONFIG flag to skip importing these exports
+  # when the target platform does not support shared library.
----------------
petrhosek wrote:

```suggestion
  # Exports from LLVM and Clang may contain shared libraries. When targeting
  # baremetal platforms that lack shared library support, importing such
  # exports unrestrictedly will trigger an error. Set
  # LLVM_OMIT_EXPORTS_FROM_CONFIG flag to skip importing these exports
  # when the target platform does not support shared libraries.
```

https://github.com/llvm/llvm-project/pull/210496