I know this is an old question, but he figured out how to use WebApplications.targets on OSX, so itβs worth the answer anyway. Webapplication.targets included in the current version of Mono (5.x), so now all you have to do is install VSToolsPath and everything should work.
If you use the standard bash shell, then the .profile file is where you can put it:
export VSToolsPath=/Library/Frameworks/Mono.framework/Versions/Current/lib/mono/xbuild/Microsoft/VisualStudio/v15.0/
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