RFR: 8145936 - Fixes required to build and run Zero arm64 iOS Mobile JRE

[Bob Vandette]

http://cr.openjdk.java.net/~bobv/8145936/webrev.00/

Please review the following fixes that were required to complete the 
initial bringup of the iOS ARM64 Zero Java runtime in the JDK 9 Mobile/dev forest.

1. Change the VAR_CPU_ARCH for 64-bit to "arm" from “aarch64 in order to 
ensure that OPENJDK_TARGET_CPU_ARCH is set to CPU architecture family
and not specific architecture version.  This is the way x86/x86_x64 is also handled.

2. Add the SocketOption and UnixConstant template files into the JDK repo.
These are required for cross compilation builds since the genSocketOption
and genUnixConstants programs cannot be run on the build system.

3. Add a macosx directory for iOS build in the NIO makefile.
Exclude the UTIFileTypeDetector.c file from the iOS build since it
is dependent on a Framework that is not available in iOS.  We probably 
should remove the entire MacOSXFileSystemProvider set of classes.
Currently the default provider for iOS is Bsd.

Bob Vandette