Replaced strerror_r XSI-compliant to GNU-specific version as esp-idf …

[izmmisha]

…depends on _GNU_SOURCE

fixed strerror_r function mismatch

/home/im/esp-apple-homekit-adk/port/src/HAPPlatformLog.c: In function 'HAPPlatformLogPOSIXError':
/home/im/esp-apple-homekit-adk/port/src/HAPPlatformLog.c:60:13: warning: initialization of 'int' from 'char *' makes integer from pointer without a cast [-Wint-conversion]
     int e = strerror_r(errorNumber, errorString, sizeof errorString);
             ^~~~~~~~~~

This problem leading errors such as #11

[skanico]

This solved my problem. No more crashes. Thanks @izmmisha

[shahpiyushv]

This fix has now been merged in this commit. Thanks for the contribution.