[MCA] Anchoring the vtable of CustomBehaviour

Put the dtor of mca::CustomBehaviour into the cpp file to avoid
undefined vtable when linking libLLVMMCACustomBehaviourAMDGPU as shared
library.

Differential Revision: https://reviews.llvm.org/D104401

llvm/include/llvm/MCA/CustomBehaviour.h

@@ -63,7 +63,7 @@ public:
                   const MCInstrInfo &MCII)
       : STI(STI), SrcMgr(SrcMgr), MCII(MCII) {}
 
-  virtual ~CustomBehaviour() {}
+  virtual ~CustomBehaviour();
 
   // Before the llvm-mca pipeline dispatches an instruction, it first checks
   // for any register or resource dependencies / hazards. If it doesn't find

llvm/lib/MCA/CustomBehaviour.cpp

@@ -16,6 +16,8 @@
 namespace llvm {
 namespace mca {
 
+CustomBehaviour::~CustomBehaviour() {}
+
 unsigned CustomBehaviour::checkCustomHazard(ArrayRef<InstRef> IssuedInst,
                                             const InstRef &IR) {
   // 0 signifies that there are no hazards that need to be waited on

llvm/tools/llvm-mca/lib/AMDGPU/CMakeLists.txt

@@ -6,6 +6,7 @@ include_directories(
 set(LLVM_LINK_COMPONENTS
   AMDGPU
   Core
+  MCA
   Support
   )