LLVM_ENABLE_EH is a global option, not a target property. For a single target, it’s more appropriate to use LLVM_REQUIRES_EH, which is also a variable you’ll need to set before calling add_llvm_component_library. You can do something like
set(LLVM_REQUIRES_EH_ORIGINAL ${LLVM_REQUIRES_EH})
set(LLVM_REQUIRES_EH YES)
add_llvm_component_library(LLVMTargetLibrary
TargetFile1.cpp
TargetFile2.cpp
)
set(LLVM_REQUIRES_EH ${LLVM_REQUIRES_EH_ORIGINAL})
The implementation for this functionality lives in llvm/cmake/modules/AddLLVM.cmake [1], where you can see what effect LLVM_REQUIRES_EH has.
[1] https://github.com/llvm/llvm-project/blob/master/llvm/cmake/modules/AddLLVM.cmake