osxrelocator: improve relocation for .Net apps
osxrelocator: improve relocation for .Net apps

.Net applications in macOS are started with the mono command
being the @executable_path the path where mono is installed
/Library/Frameworks/Mono.framework/Commands/mono
With the current relocation system, libraries in the mono installed
will be used over the ones in the output directory so applications
can't distribute their own version of glib or gtk+.
Adding '.' as the first path allows NuGet packages provide native
runtime dependencies to ship their own versions of libraries.

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