gtest install dir messes things up

[fmauch]

gtest seems to install its targets where it shouldn't. This caused problems reported in ros-melodic-arch/ros-melodic-tf#6 and got fixed upstream (for noetic) in ros/catkin@7fa3eb3

Should we

• patch our melodic catkin version
• Use the noetic catkin version for melodic on Archlinux
• Try to get it included upstream (See Fix problem with Googletest's LIBRARY_OUTPUT_DIRECTORY ros/catkin#1135 (comment))

[bionade24]

I remember there was a technical reason why we dowgraded the major version back to 7. Let's see if upstream responds. If this doesn't affect the gtest version shipped with melodic normally and they won't patch it in 0.7, we have to reevaluate.