Add build instructions for OSX without XCode

[xavriley]

I was able to install libmei without XCode using the following commands:

git clone https://github.com/DDMAL/libmei.git
cd libmei
mkdir build && cd build
brew install cmake
brew install ossp-uuid
cmake .. -DCMAKE_FIND_FRAMEWORK=LAST
make
make install

This could be useful to others who don't normally use XCode. It might also help to streamline the creation of a Homebrew package.

[ahankinson]

Thanks. Can I ask what you are using libmei for? It hasn’t been updated in a while and I’m trying to figure out if it’s still useful, or whether there are now better ways of working with MEI files.