Others have responded, but I don't think they get the gist of this question exactly.
C, C++, etc are just as retargetable as LLVM because you can take IR code, C, or C++ code (assuming standards compliance) and get a machine dependent binary anywhere you have a working compiler / assembler / linker stack. Clang uses LLVM as a translation layer for C and C++ because LLVM IR code is much more machine-like and makes writing the final assembler / linker easier, since you are just effectively translating abstracted assembly into machine specific assembly, instead of an object oriented / procedural dialect language into machine instructions.
C, C++, etc are just as retargetable as LLVM because you can take IR code, C, or C++ code (assuming standards compliance) and get a machine dependent binary anywhere you have a working compiler / assembler / linker stack. Clang uses LLVM as a translation layer for C and C++ because LLVM IR code is much more machine-like and makes writing the final assembler / linker easier, since you are just effectively translating abstracted assembly into machine specific assembly, instead of an object oriented / procedural dialect language into machine instructions.