[5.10] Revert 'Add missing dependency (#1414)'

[finagolfin]

Cherrypick of #1481

Explanation: The llbuild executable is not a dependency of this library.

Scope: Removes wrongly added llbuild dependency

Issue: None

Risk: low, as less code is built after this

Testing: Passed all CI on trunk

Reviewer: @artemcm

[artemcm]

cc @nkcsgexi

[artemcm]

@swift-ci test

[finagolfin]

Ping, another CI run and then this can go in?

[finagolfin]

@neonichu, would be good to get this in before the winter break.

[finagolfin]

@kateinoigakukun, please run the CI on this.

[kateinoigakukun]

@swift-ci Please test

[finagolfin]

Another CI run needed here.

@artemcm, looks like this is only held up on 5.10 manager approval, is there someone else who can review?

[finagolfin]

@kateinoigakukun, one last CI run and we can get this in.

[kateinoigakukun]

@swift-ci test

[finagolfin]

Ping @nkcsgexi, ready for review and merge.

[finagolfin]

Ping @nkcsgexi, still looking for review here and I figure you are the manager for this repo.

[finagolfin]

Ping @artemcm, can we go ahead and get this in?

[finagolfin]

@bnbarham, would you review this tiny pull for 5.10?

[finagolfin]

@neonichu, this revert of your pull has been stuck for months now, can you review or alert whoever needs to decide?

[finagolfin]

Pinging @bnbarham again, can we get this in now?

[finagolfin]

Ping @DougGregor, there is no 5.10 release manager listed for this repo on the forum, but maybe it falls under your purview as part of the compiler.

This is just a small build cleanup that shouldn't break anything, been working fine in trunk for almost three months now.

[finagolfin]

Ping @neonichu, can you notify someone who can get this in?

[finagolfin]

Pinging @shahmishal, could you weigh in on this cleanup?

[finagolfin]

@shahmishal, if you're preparing a 5.10 patch release, would be good to get this cleanup in. It was merged into trunk six months ago and has had no deleterious effect.