Filter: Fix gnuplot shebang lines

[cclauss]

https://github.com/ArduPilot/ardupilot/pull/30351#pullrequestreview-2928927779

The shebang lines are actually incorrect in the .gnu files

% git grep gnuplot

Tools/Replay/plotit.sh:gnuplot _plot.gnu  # Not a shebang line.
libraries/Filter/tests/plot_harmonics.gnu:#!/usr/bin/gnuplot -persist
libraries/Filter/tests/plot_harmonictest2.gnu:#!/usr/bin/gnuplot -persist
libraries/Filter/tests/plot_harmonictest3.gnu:#!/usr/bin/gnuplot -persist
libraries/Filter/tests/plot_harmonictest4.gnu:#!/usr/bin/gnuplot -persist
libraries/Filter/tests/plot_harmonictest5.gnu:#!/usr/bin/gnuplot -persist

% git diff # In 5 files.

- #!/usr/bin/gnuplot -persist
+ #!/usr/bin/env -S gnuplot -persist

[cclauss]

Can a maintainer please rerun the failing test?

#!/usr/bin/env -S gnuplot -persist

[peterbarker]

Can a maintainer please rerun the failing test?

#!/usr/bin/env -S gnuplot -persist

I've re-tested and things are now working.

Please avoid pushing the testing burden onto other people. It's usually more work than the initial patches.

[cclauss]

Thanks for your patience and the reviews!

Please avoid pushing the testing burden onto other people. It's usually more work than the initial patches.

Agreed. Sorry. brew install gnuplot would have installed a lot of extra gorp onto my Mac, which I wanted to avoid. I should have tested this in a Docker container.

On the bright side, I now have that #!/usr/bin/env -S syntax firmly planted in my head and am using it in other testing.

• https://github.com/ArduPilot/MAVProxy/pull/1588#issuecomment-2986540996