Add support for arm-based Mac OS

[raducoravu]

Probably a new "libhunspell-darwin-arm.dylib" would be needed as JNA will shortly add support for arm-based darwin:
java-native-access/jna#1297

[hshafie]

Very interested too.

[raducoravu]

Added some notes made by my colleague who compiled the Hunspell code to create a library for darwyn-arm for our product.

He says he used Xcode for compiling and started from these instructions listed here working on a Mac silicon:
https://github.com/hunspell/hunspell#compiling-on-osx-and-macos

The SDKROOT needs to be set to the Xcode SDK before running configure by doing this in the comand line:

   export SDKROOT="/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk"

The flags for the configure command need to be changed as follows:

CFLAGS='-arch arm64 -g -O2' CXXFLAGS='-arch arm64 -g -O2' CPPFLAGS='-arch arm64 -g -O2' LDFLAGS='-arch arm64' bash configure --host=arm64-apple-darwin