HADOOP-6864 uses the setnetgrent function in a way which is not compatible with BSD APIs, where the call returns void rather than int. This prevents the native libs from building on OSX, for example.
Fix build native library on mac osx
getgrouplist() in getGroup.c is not portable
setnetgrent in native code is not portable
Provide a JNI-based implementation of ShellBasedUnixGroupsNetgroupMapping (implementation of GroupMappingServiceProvider)
NativeIO.java flags and identifiers must be set correctly for each platform, not hardcoded to their Linux values