aws-c-auth: update to 0.6.21
aws-c-auth: update to 0.6.21

oscarfv/MINGW-packages,stahta01/MINGW-packages,stahta01/MINGW-packages,stahta01/MINGW-packages,oscarfv/MINGW-packages,oscarfv/MINGW-packages,oscarfv/MINGW-packages,oscarfv/MINGW-packages,oscarfv/MINGW-packages,stahta01/MINGW-packages,stahta01/MINGW-packages,stahta01/MINGW-packages