[BOLT][NFC] Reduce Target/{AArch64,X86} dependencies

[Amir]

Summary

We don't actually depend on entire X86/AArch64 components that pull in CodeGen,
SelectionDAG etc., just the Desc part with opcode and other definitions.

Note that it doesn't decouple BOLT from these components - we still pull in X86
and AArch64 from top-level llvm-bolt dependencies as we use assembler and
disassembler. It's difficult to reduce these as this requires non-trivial
changes to X86/AArch64 components themselves (e.g. moving out AsmPrinter).

[rafauler]

LGTM

bolt/lib/Target/AArch64/CMakeLists.txt

 set(LLVM_LINK_COMPONENTS
   BOLTCore
   MC
-  Object
   Support
-  ${LLVM_TARGETS_TO_BUILD}
+  AArch64Desc
   )
 
 add_llvm_library(LLVMBOLTTargetAArch64
   AArch64MCPlusBuilder.cpp
 
   DEPENDS
-  intrinsics_gen
   AArch64CommonTableGen
   )
 
-include_directories(${LLVM_MAIN_SRC_DIR}/lib/Target/AArch64 ${LLVM_BINARY_DIR}/lib/Target/AArch64)
+include_directories(
+  ${LLVM_MAIN_SRC_DIR}/lib/Target/AArch64
+  ${LLVM_BINARY_DIR}/lib/Target/AArch64
+  )

bolt/lib/Target/X86/CMakeLists.txt

 set(LLVM_LINK_COMPONENTS
   BOLTCore
   BOLTUtils
   MC
-  Object
   Support
-  ${LLVM_TARGETS_TO_BUILD}
+  X86Desc
   )
 
 add_llvm_library(LLVMBOLTTargetX86
   X86MCPlusBuilder.cpp
 
   DEPENDS
-  intrinsics_gen
   X86CommonTableGen
   )
 
-include_directories(${LLVM_MAIN_SRC_DIR}/lib/Target/X86 ${LLVM_BINARY_DIR}/lib/Target/X86)
+include_directories(
+  ${LLVM_MAIN_SRC_DIR}/lib/Target/X86
+  ${LLVM_BINARY_DIR}/lib/Target/X86
+  )