[Build] Checkout equinox and equinox.binaries repositories side by side

[HannesWell]

in Jenkins pipeline.

This is a prerequisite for https://github.com/eclipse-equinox/equinox/pull/603

[github-actions[bot]]

Test Results

   87 files  ±0     87 suites  ±0   36m 33s :stopwatch: -6s 2 199 tests ±0  2 152 :white_check_mark: ±0   47 :zzz: ±0  0 :x: ±0  6 729 runs  ±0  6 586 :white_check_mark: ±0  143 :zzz: ±0  0 :x: ±0 

Results for commit 7574b9e0. ± Comparison against base commit 5fa3aed0.