message: waf configure --use-system-clang, prefer bld.env.get_flat('CXX') over clang inferred from llvm-config'
  Fixes Credit to
diff: @@ -310,7 +310,13 @@ def build(bld):
  output = str(subprocess.check_output(
  [bld.env['llvm_config'], '--bindir'],
  stderr=subprocess.STDOUT).decode()).strip()
  +
  + # Use --check-cxx-compiler value if it is "clang".
  + # See https://github.com/jacobdufault/cquery/issues/237
  + clang = bld.env.get_flat('CXX')
  + if 'clang' not in clang:
  clang = os.path.join(output, 'clang')
  +
  rpath = str(subprocess.check_output(
  [bld.env['llvm_config'], '--libdir'],
  stderr=subprocess.STDOUT).decode()).strip()
  