cmake: improvements to cross-compiling for Windows

* don't unconditionally pass -lz3 for mingw builds. If mingw builds
   require this then the llvm-config executable should put it as part of
   --system-libs. If there is a bug and it does not do that, and we need
   a workaround, then the workaround should be an explicit cmake option.
 * don't link libstage2.a against -lntdll. This causes zig to set
   `builtin.link_mode == .Dynamic` and include the TLS definitions,
   which then collide with the mingw-w64 symbols. This should probably
   be addressed separately, but for now this solves the problem and
   there is no reason to link a static library against a DLL.
 * Findllvm.cmake no longer treats the libraries as "optional" and will
   emit a cmake error if one is not found. Additionally, the
   not-required LLVM library LLVMTableGen is omitted.

CMakeLists.txt

@@ -365,7 +365,7 @@ if(ZIG_STATIC)
     endif()
 else()
     if(MINGW)
-        set(EXE_LDFLAGS "${EXE_LDFLAGS} -lz3")
+        set(EXE_LDFLAGS "${EXE_LDFLAGS}")
     endif()
 endif()
 
@@ -429,11 +429,6 @@ if("${CMAKE_BUILD_TYPE}" STREQUAL "Debug")
 else()
     set(LIBSTAGE2_RELEASE_ARG --release-fast --strip)
 endif()
-if(WIN32)
-    set(LIBSTAGE2_WINDOWS_ARGS "-lntdll")
-else()
-    set(LIBSTAGE2_WINDOWS_ARGS "")
-endif()
 
 set(BUILD_LIBSTAGE2_ARGS "build-lib"
     "src-self-hosted/stage2.zig"
@@ -447,7 +442,6 @@ set(BUILD_LIBSTAGE2_ARGS "build-lib"
     --bundle-compiler-rt
     -fPIC
     -lc
-    ${LIBSTAGE2_WINDOWS_ARGS}
 )
 
 if("${ZIG_TARGET_TRIPLE}" STREQUAL "native")

cmake/Findllvm.cmake

@@ -144,9 +144,7 @@ else()
         /mingw64/lib
         /c/msys64/mingw64/lib
         c:\\msys64\\mingw64\\lib)
-      if(LLVM_${_prettylibname_}_LIB)
-        set(LLVM_LIBRARIES ${LLVM_LIBRARIES} ${LLVM_${_prettylibname_}_LIB})
-      endif()
+      set(LLVM_LIBRARIES ${LLVM_LIBRARIES} ${LLVM_${_prettylibname_}_LIB})
     endmacro(FIND_AND_ADD_LLVM_LIB)
 
     # This list can be re-generated with `llvm-config --libfiles` and then
@@ -154,7 +152,6 @@ else()
     # `llvm-config` here because we are cross compiling.
     FIND_AND_ADD_LLVM_LIB(LLVMXRay)
     FIND_AND_ADD_LLVM_LIB(LLVMWindowsManifest)
-    FIND_AND_ADD_LLVM_LIB(LLVMTableGen)
     FIND_AND_ADD_LLVM_LIB(LLVMSymbolize)
     FIND_AND_ADD_LLVM_LIB(LLVMDebugInfoPDB)
     FIND_AND_ADD_LLVM_LIB(LLVMOrcJIT)