fix top level Makefile for AmberTools 20 and enable tests

[akesandgren]

(created using eb --new-pr)

Depends on easybuilders/easybuild-easyblocks#2781

[akesandgren]

@boegelbot Please test @ generoso

[boegelbot]

@akesandgren: Request for testing this PR well received on login1

PR test command 'EB_PR=16150 EB_ARGS= /opt/software/slurm/bin/sbatch --job-name test_PR_16150 --ntasks=4 ~/boegelbot/eb_from_pr_upload_generoso.sh' executed!

• exit code: 0
• output:

Submitted batch job 9093

Test results coming soon (I hope)...

- notification for comment with ID 1232794918 processed

Message to humans: this is just bookkeeping information for me,
it is of no use to you (unless you think I have a bug, which I don't).

[boegelbot]

Test report by @boegelbot
SUCCESS
Build succeeded for 1 out of 1 (1 easyconfigs in total)
cns2 - Linux Rocky Linux 8.5, x86_64, Intel(R) Xeon(R) CPU E5-2667 v3 @ 3.20GHz (haswell), Python 3.6.8
See https://gist.github.com/16f368b42dffba4d55bdb8b0df5a848e for a full test report.

[boegel]

lgtm

[boegel]

Test report by @boegel
SUCCESS
Build succeeded for 6 out of 6 (1 easyconfigs in total)
node3114.skitty.os - Linux RHEL 8.4, x86_64, Intel(R) Xeon(R) Gold 6140 CPU @ 2.30GHz (skylake_avx512), Python 3.6.8
See https://gist.github.com/aafd71f660c3e4ba55d76d3d4bcb4e7e for a full test report.

[boegel]

Going in, thanks @akesandgren!