[lldb] Fix Python 3 incompatibility in API/lit.cfg.py

This code path is only taken on the sanitized bot, where it caused a
TypeError: "Can't mix strings and bytes in path components".

lldb/test/API/lit.cfg.py

@@ -27,7 +27,8 @@ if 'Address' in config.llvm_use_sanitizer:
   if 'Darwin' in config.host_os and 'x86' in config.host_triple:
     import subprocess
     resource_dir = subprocess.check_output(
-        [config.cmake_cxx_compiler, '-print-resource-dir']).strip()
+        [config.cmake_cxx_compiler,
+         '-print-resource-dir']).decode('utf-8').strip()
     runtime = os.path.join(resource_dir, 'lib', 'darwin',
                            'libclang_rt.asan_osx_dynamic.dylib')
     config.environment['DYLD_INSERT_LIBRARIES'] = runtime