fix: use rpath in engine dylib

[dandanlen]

This fixes an issue with the engine dylib file that was preventing it from running on mac localnets.

The dylib install path was previously set to a local path on my machine.
Now it's correctly set to a relative path.

The engine lib build script already do this correctly on main, but that change hasn't been ported to the release branch. Hence the release version 1.4.5 libs were compiled with absolute paths instead of relative paths.

Before:

otool -L old-engine-dylib/libchainflip_engine_v1_4_5.dylib | head -2
old-engine-dylib/libchainflip_engine_v1_4_5.dylib:
        /Users/dan/[...]/old-engine-dylib/libchainflip_engine_v1_4_5.dylib (compatibility version 0.0.0, current version 0.0.0)

After:

otool -L old-engine-dylib/libchainflip_engine_v1_4_5.dylib | head -2
old-engine-dylib/libchainflip_engine_v1_4_5.dylib:
        @rpath/old-engine-dylib/libchainflip_engine_v1_4_5.dylib (compatibility version 0.0.0, current version 0.0.0)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 72%. Comparing base (1ef2593) to head (f4bacec).
Report is 3 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #5031   +/-   ##
=====================================
- Coverage     72%     72%   -0%     
=====================================
  Files        431     431           
  Lines      74778   74775    -3     
  Branches   74778   74775    -3     
=====================================
- Hits       53536   53487   -49     
- Misses     18396   18431   +35     
- Partials    2846    2857   +11     

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[kylezs]

It should be @rpath/libchainflip-engine... and not @rpath/old-engine-dylib/libchainflip-engine...

[kylezs]

FYI - this won't need to be set manually after 1.5 (i.e. when 1.5 is the "old" dylib) - as it's now part of the build. rpath = true in the Cargo.toml now.