[Buildbot] Remove outdated LLVM_AR parameter for Windows to Linux Cross toolchain builders.

[vvereschaka]

Summary

Removed outdated LLVM_AR parameters for the cmake cache file used to build Windows to Linux cross toolchain builds.

[gkistanova]

LGTM

zorg/buildbot/builders/XToolchainBuilder.py

def getCmakeWithMSVCBuildFactory(
 
     if vs:
         # Configure MSVC environment if requested.
         f.addStep(SetPropertyFromCommand(
             command=builders_util.getVisualStudioEnvironment(vs, None),
             extract_fn=builders_util.extractVSEnvironment))
         merged_env = Property('vs_env')
 
-    # Since this is a build of a cross toolchain, we build only the host-side
-    # tools first by the host system compiler. Libraries will be cross-compiled.
-    cmake_args.append(InterpolateToPosixPath(
-        '-DLLVM_AR=%(builddir)s/' + f.obj_dir + '/bin/llvm-ar.exe')),
-
     CmakeCommand.applyDefaultOptions(cmake_args, [
         ('-G', 'Ninja'),
         ('-DLLVM_ENABLE_PROJECTS=', 'llvm;clang;clang-tools-extra;lld'),
         ('-DCMAKE_BUILD_TYPE=', 'Release'),
         ('-DCMAKE_CXX_FLAGS=', '-D__OPTIMIZE__'),
         ('-DLLVM_ENABLE_ASSERTIONS=', 'ON'),
         ('-DLLVM_LIT_ARGS=', '-v -vv'),
         ])