CXX feature checks fails

I am facing a build error with PyTorch with a custom path installed gcc (6.1.0). The build command fails at

```
CMake Error at third_party/benchmark/CMakeLists.txt:231 (message):
Failed to determine the source files for the regular expression backend
```
and that is

```
# C++ feature checks
# Determine the correct regular expression engine to use
cxx_feature_check(STD_REGEX)
cxx_feature_check(GNU_POSIX_REGEX)
cxx_feature_check(POSIX_REGEX)
if(NOT HAVE_STD_REGEX AND NOT HAVE_GNU_POSIX_REGEX AND NOT HAVE_POSIX_REGEX)
message(FATAL_ERROR "Failed to determine the source files for the regular expression backend")
endif()
```
However, it seems that there is not verbosity for [cxx checks](https://github.com/google/benchmark/blob/505be96ab23056580a3a2315abba048f4428b04e/cmake/CXXFeatureCheck.cmake).
Is there any idea on how to narrow the problem?