Converting "env" to the name of the program

[gholmann16]

I'm currently writing an appimage manager using libappimage, and I was testing integrating audacity. In audacity .desktop file, it's default Exec is Exec=env UBUNTU_MENUPROXY=0 audacity %F. When I use register_in_system(), the appimage gets stored in local share applications as, Exec=/etc/neptune/bin/audacity UBUNTU_MENUPROXY=0 audacity %F where /etc/neptune/bin is where audacity is located. This results in audacity trying and failing to open UBUNTU_MENUPROXY and audacity as music files and sees that they don't exist. That's all.