Check where testpackage is installed before attenmpting to run integration tests

[lossius]

Quoting mail from @tap :

I get the following crash at the end of building the Max stuff for Jamoma:
build.rb:151:in `chdir': No such file or directory - /Applications/Max 6.1/packages/testpackage/ruby (Errno::ENOENT)

​I get this crash, presumably, because I don't have the testpackage installed there -- this is not where user packages are supposed to be installed. User packages should be installed at ~/Max/Packages.

It would also be better if the script checked if the script exists instead of crashing. Or at least wrap this block in a "begin - rescue - end" block.

Quoting mail from @hems :

If someone need example o File.exists / "begin - rescuse - end" block, have a look here: https://github.com/jamoma/Jamoma/blob/dev/build.rb#L193-L205 should be a good starting point

I guess we should look for the testpackage in Applications/Max 6.1 (provided that we are on OSX), as well as ~/Max/Packages. I don't necsessarily agree that Packages are not supposed to be installed in /Applications/Max 6.1/packages, that's what I'd do if I want to make them available for all users on a Mac with several users.

[tap]

In a perfect world, everything in the Max folder should be considered read-only. The permissions model of OSX, for example, is that this folder should not be writable. It is a slow-moving process over the last number of years, but Max is slowly adapting to this model.

The "correct" location for packages shared amongst all users should then be /Users/Shared/Max/Packages -- except that in our oversight we didn't implement that (yet). I'll create a ticket for at C74.