Reland [Clang][Cmake] fix libtool duplicate member name warnings (#133850)

fixes #133199

As of the third commit the fix to the linker missing references in
`Targets/DirectX.cpp` found in
#133776 was fixed by moving
`HLSLBufferLayoutBuilder.cpp` to `clang/lib/CodeGen/Targets/`.

It fixes the circular reference issue found in
#133619 for all
`-DBUILD_SHARED_LIBS=ON` builds by removing `target_link_libraries` from
the sub directory cmake files.

testing for amdgpu offload was done via
`cmake -B ../llvm_amdgpu -S llvm -GNinja -C
offload/cmake/caches/Offload.cmake -DCMAKE_BUILD_TYPE=Release`

PR #132252 Created a second
file that shared <TargetName>.cpp in clang/lib/CodeGen/CMakeLists.txt

For example There were two AMDGPU.cpp's one in TargetBuiltins and the
other in Targets. Even though these were in different directories
libtool warns that it might not distinguish them because they share the
same base name.

There are two potential fixes. The easy fix is to rename one of them and
keep one cmake file. That solution though doesn't future proof this
problem in the event of a third <TargetName>.cpp and it seems teams want
to just use the target name

#132252 (comment).

The alternative fix that this PR went with is to seperate the cmake
files into their own sub directories as static libs.

Author: farzonl

Diff for: clang/lib/CodeGen/CMakeLists.txt

@@ -107,7 +107,6 @@ add_clang_library(clangCodeGen
   ConstantInitBuilder.cpp
   CoverageMappingGen.cpp
   ItaniumCXXABI.cpp
-  HLSLBufferLayoutBuilder.cpp
   LinkInModulesPass.cpp
   MacroPPCallbacks.cpp
   MicrosoftCXXABI.cpp
@@ -116,43 +115,7 @@ add_clang_library(clangCodeGen
   PatternInit.cpp
   SanitizerMetadata.cpp
   SwiftCallingConv.cpp
-  TargetBuiltins/ARM.cpp
-  TargetBuiltins/AMDGPU.cpp
-  TargetBuiltins/Hexagon.cpp
-  TargetBuiltins/NVPTX.cpp
-  TargetBuiltins/PPC.cpp
-  TargetBuiltins/RISCV.cpp
-  TargetBuiltins/SPIR.cpp
-  TargetBuiltins/SystemZ.cpp
-  TargetBuiltins/WebAssembly.cpp
-  TargetBuiltins/X86.cpp
   TargetInfo.cpp
-  Targets/AArch64.cpp
-  Targets/AMDGPU.cpp
-  Targets/ARC.cpp
-  Targets/ARM.cpp
-  Targets/AVR.cpp
-  Targets/BPF.cpp
-  Targets/CSKY.cpp
-  Targets/DirectX.cpp
-  Targets/Hexagon.cpp
-  Targets/Lanai.cpp
-  Targets/LoongArch.cpp
-  Targets/M68k.cpp
-  Targets/MSP430.cpp
-  Targets/Mips.cpp
-  Targets/NVPTX.cpp
-  Targets/PNaCl.cpp
-  Targets/PPC.cpp
-  Targets/RISCV.cpp
-  Targets/SPIR.cpp
-  Targets/Sparc.cpp
-  Targets/SystemZ.cpp
-  Targets/TCE.cpp
-  Targets/VE.cpp
-  Targets/WebAssembly.cpp
-  Targets/X86.cpp
-  Targets/XCore.cpp
   VarBypassDetector.cpp
 
   DEPENDS
@@ -170,4 +133,16 @@ add_clang_library(clangCodeGen
   clangFrontend
   clangLex
   clangSerialization
+  clangCodeGenTargetBuiltins
+  clangCodeGenTargets
   )
+
+  target_include_directories(clangCodeGen
+    PUBLIC
+    ${CMAKE_CURRENT_SOURCE_DIR}
+    ${CMAKE_CURRENT_SOURCE_DIR}/TargetBuiltins
+    ${CMAKE_CURRENT_SOURCE_DIR}/Targets
+  )
+  
+  add_subdirectory(TargetBuiltins)
+  add_subdirectory(Targets)

Diff for: clang/lib/CodeGen/TargetBuiltins/AMDGPU.cpp

@@ -1,4 +1,4 @@
-//===------- AMDCPU.cpp - Emit LLVM Code for builtins ---------------------===//
+//===------- AMDGPU.cpp - Emit LLVM Code for builtins ---------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.

Diff for: clang/lib/CodeGen/TargetBuiltins/CMakeLists.txt

@@ -0,0 +1,14 @@
+include_directories(${CMAKE_CURRENT_SOURCE_DIR}/..)
+
+add_clang_library(clangCodeGenTargetBuiltins STATIC
+  ARM.cpp
+  AMDGPU.cpp
+  Hexagon.cpp
+  NVPTX.cpp
+  PPC.cpp
+  RISCV.cpp
+  SPIR.cpp
+  SystemZ.cpp
+  WebAssembly.cpp
+  X86.cpp
+)

Diff for: clang/lib/CodeGen/Targets/CMakeLists.txt

@@ -0,0 +1,31 @@
+include_directories(${CMAKE_CURRENT_SOURCE_DIR}/..)
+
+add_clang_library(clangCodeGenTargets STATIC
+  AArch64.cpp
+  AMDGPU.cpp
+  ARC.cpp
+  ARM.cpp
+  AVR.cpp
+  BPF.cpp
+  CSKY.cpp
+  DirectX.cpp
+  HLSLBufferLayoutBuilder.cpp
+  Hexagon.cpp
+  Lanai.cpp
+  LoongArch.cpp
+  M68k.cpp
+  MSP430.cpp
+  Mips.cpp
+  NVPTX.cpp
+  PNaCl.cpp
+  PPC.cpp
+  RISCV.cpp
+  SPIR.cpp
+  Sparc.cpp
+  SystemZ.cpp
+  TCE.cpp
+  VE.cpp
+  WebAssembly.cpp
+  X86.cpp
+  XCore.cpp
+)