Revert "TargetMachine: Merge TargetMachine and LLVMTargetMachine"

Reverting to investigate layering effects of MCJIT not linking
libCodeGen but using TargetMachine::getNameWithPrefix() breaking the
lldb bots.

This reverts commit r315633.

llvm-svn: 315637
diff --git a/llvm/lib/Target/Nios2/Nios2TargetMachine.cpp b/llvm/lib/Target/Nios2/Nios2TargetMachine.cpp
index 6155d0b..7370dac 100644
--- a/llvm/lib/Target/Nios2/Nios2TargetMachine.cpp
+++ b/llvm/lib/Target/Nios2/Nios2TargetMachine.cpp
@@ -42,8 +42,8 @@
                                        Optional<Reloc::Model> RM,
                                        Optional<CodeModel::Model> CM,
                                        CodeGenOpt::Level OL, bool JIT)
-    : TargetMachine(T, computeDataLayout(), TT, CPU, FS, Options,
-                    getEffectiveRelocModel(RM), *CM, OL) {}
+    : LLVMTargetMachine(T, computeDataLayout(), TT, CPU, FS, Options,
+                        getEffectiveRelocModel(RM), *CM, OL) {}
 
 Nios2TargetMachine::~Nios2TargetMachine() {}