Expression: add missing linkage to RuntimeDyld component

Add missing linkage from lldbExpression library to LLVMRuntimeDyld.
Otherwise the build against shared LLVM libraries fails with:

    lib64/liblldbExpression.a(IRExecutionUnit.cpp.o):IRExecutionUnit.cpp:function llvm::RTDyldMemoryManager::deregisterEHFrames(unsigned char*, unsigned long, unsigned long): error: undefined reference to 'llvm::RTDyldMemoryManager::deregisterEHFramesInProcess(unsigned char*, unsigned long)'

Differential Revision: https://reviews.llvm.org/D31367

llvm-svn: 298776