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

[Petr Hosek via cfe-commits]

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@@ -12,8 +12,13 @@ set(CLANG_INCLUDE_DIRS "@CLANG_CONFIG_INCLUDE_DIRS@")
 set(CLANG_LINK_CLANG_DYLIB "@CLANG_LINK_CLANG_DYLIB@")
 set(CLANG_DEFAULT_LINKER "@CLANG_DEFAULT_LINKER@")
 
-# Provide all our library targets to users.
- at CLANG_CONFIG_INCLUDE_EXPORTS@
+# Provide all our library targets to users. Skip when
+# LLVM_OMIT_EXPORTS_FROM_CONFIG flag is set. Runtimes build do not need these.
+# These exports may contain shared libraries and they are causing cmake errors
+# when the target platform is baremetal, which lack shared library support.
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petrhosek wrote:

```suggestion
# Provide all our library targets to users. Skip when
# LLVM_OMIT_EXPORTS_FROM_CONFIG flag is set. Runtimes build do not need these.
# These exports may contain shared libraries which trigger to an import error
# when the target platform lacks shared library support.
```

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