[llvm] Export LLVM_USE_SPLIT_DWARF in LLVMConfig.cmake

Export LLVM_USE_SPLIT_DWARF in LLVMConfig.cmake so that it can be used
from standalone builds of clang and lldb. Currently, there is no way for
standalone builds to know whether this option was set which means that
it only applies to LLVM.

Differential revision: https://reviews.llvm.org/D89282

llvm/cmake/modules/LLVMConfig.cmake.in

@@ -16,6 +16,8 @@ set(LLVM_USE_CRT_MINSIZEREL @LLVM_USE_CRT_MINSIZEREL@)
 set(LLVM_USE_CRT_RELEASE @LLVM_USE_CRT_RELEASE@)
 set(LLVM_USE_CRT_RELWITHDEBINFO @LLVM_USE_CRT_RELWITHDEBINFO@)
 
+set(LLVM_USE_SPLIT_DWARF @LLVM_USE_SPLIT_DWARF@)
+
 set(LLVM_COMMON_DEPENDS @LLVM_COMMON_DEPENDS@)
 
 set(LLVM_AVAILABLE_LIBS @LLVM_AVAILABLE_LIBS@)