Add dev thanks env var via CI

[nbolton]

Upstream: https://github.com/symless/synergy/pull/7452

[github-actions]

Test results

See workflow run for test output.

Job name	Unit tests	Integration tests
linux-debian-12-arm64	✅ Pass	✅ Pass
linux-fedora-40-arm64	✅ Pass	✅ Pass
macos-14-arm64	✅ Pass	✅ Pass
linux-ubuntu-22.04-amd64	✅ Pass	✅ Pass
linux-almalinux-9-amd64	✅ Pass	✅ Pass
linux-rockylinux-9-amd64	✅ Pass	✅ Pass
linux-debian-12-amd64	✅ Pass	✅ Pass
linux-fedora-40-amd64	✅ Pass	✅ Pass
linux-opensuse-amd64	✅ Pass	✅ Pass
linux-ubuntu-24.04-amd64	✅ Pass	✅ Pass
linux-fedora-39-amd64	✅ Pass	✅ Pass
windows-2022-x64	✅ Pass	✅ Pass
linux-archlinux-amd64	✅ Pass	✅ Pass
linux-manjaro-amd64	✅ Pass	✅ Pass
macos-14-x64	✅ Pass	✅ Pass

[github-actions]

Valgrind summary

See workflow run for full valgrind output.

Unit tests

==3893== HEAP SUMMARY:
==3893==     in use at exit: 50,787 bytes in 333 blocks
==3893==   total heap usage: 33,596 allocs, 33,263 frees, 5,995,601 bytes allocated

==3893== LEAK SUMMARY:
==3893==    definitely lost: 334 bytes in 10 blocks
==3893==    indirectly lost: 734 bytes in 13 blocks
==3893==      possibly lost: 0 bytes in 0 blocks
==3893==    still reachable: 47,703 bytes in 289 blocks
==3893==         suppressed: 0 bytes in 0 blocks
==3893== 
==3893== ERROR SUMMARY: 28 errors from 28 contexts (suppressed: 0 from 0)

Integration tests

==3911== HEAP SUMMARY:
==3911==     in use at exit: 22,132 bytes in 76 blocks
==3911==   total heap usage: 2,409 allocs, 2,333 frees, 647,473 bytes allocated

==3911== LEAK SUMMARY:
==3911==    definitely lost: 912 bytes in 39 blocks
==3911==    indirectly lost: 80 bytes in 4 blocks
==3911==      possibly lost: 1,536 bytes in 4 blocks
==3911==    still reachable: 19,604 bytes in 29 blocks
==3911==         suppressed: 0 bytes in 0 blocks
==3911== 
==3911== ERROR SUMMARY: 44 errors from 44 contexts (suppressed: 0 from 0)

[nbolton]

Merged in upstream