Not building on GCC 7.2 (Unused variable)

[0xfede7c8]

libhttp git:(master) make
....stuff
src/httplib_error_string.c: In function ‘httplib_error_string’:
src/httplib_error_string.c:170:2: error: ignoring return value of ‘strerror_r’, declared with attribute 
warn_unused_result [-Werror=unused-result]
  strerror_r( error_code, buf, buf_len );
  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors

[Frank-Shaw-FS]

the stederror_r require you to handle the return value.