Fix error: 'WC_ERR_INVALID_CHARS' was not declared in this scope

[zm1060]

When building leveldb, add_test(NAME "leveldb_tests" COMMAND "leveldb_tests").

FAILED: third_party/benchmark/src/CMakeFiles/benchmark.dir/sysinfo.cc.obj 
D:\MingW\bin\g++.exe -DBENCHMARK_STATIC_DEFINE -DHAVE_STD_REGEX -DHAVE_STEADY_CLOCK -DUNICODE -D_UNICODE -IF:/Contribute/leveldb/cmake-build-debug/include -IF:/Contribute/leveldb/. -IF:/Contribute/leveldb/third_party/benchmark/include -IF:/Contribute/leveldb/third_party/benchmark/src -fno-exceptions -fno-rtti  -Wall  -Wextra  -Wshadow  -Wfloat-equal  -Werror  -Wsuggest-override  -pedantic  -pedantic-errors  -fstrict-aliasing  -Wno-deprecated-declarations  -Wno-deprecated  -fno-exceptions  -Wstrict-aliasing -g -std=c++11 -fvisibility=hidden -fno-keep-inline-dllexport -fdiagnostics-color=always -MD -MT third_party/benchmark/src/CMakeFiles/benchmark.dir/sysinfo.cc.obj -MF third_party\benchmark\src\CMakeFiles\benchmark.dir\sysinfo.cc.obj.d -o third_party/benchmark/src/CMakeFiles/benchmark.dir/sysinfo.cc.obj -c F:/Contribute/leveldb/third_party/benchmark/src/sysinfo.cc
F:/Contribute/leveldb/third_party/benchmark/src/sysinfo.cc: In function 'std::__cxx11::string benchmark::{anonymous}::GetSystemName()':
F:/Contribute/leveldb/third_party/benchmark/src/sysinfo.cc:432:42: error: 'WC_ERR_INVALID_CHARS' was not declared in this scope
   int len = WideCharToMultiByte(CP_UTF8, WC_ERR_INVALID_CHARS, hostname,
                                          ^~~~~~~~~~~~~~~~~~~~
F:/Contribute/leveldb/third_party/benchmark/src/sysinfo.cc:432:42: note: suggested alternative: 'MB_ERR_INVALID_CHARS'
   int len = WideCharToMultiByte(CP_UTF8, WC_ERR_INVALID_CHARS, hostname,
                                          ^~~~~~~~~~~~~~~~~~~~
                                          MB_ERR_INVALID_CHARS

[google-cla[bot]]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.