build: Optimize transitive link dep resolution

In large repositories, transitive link dependency resolution using the current
recursive algorithm can result in enough duplicate calls to cause the full
system memory space to be used up.

This commit simplifies link dep resolution by converting the currently used
recursive algorithm to an iterative one that avoids performing work more than
once. If a target's direct dependencies have already been processed, that
target will not be processed again.

These changes result in multiple orders of magnitude of improvements to dep
resolution time and memory usage in the worst case.

Co-authored-by: Xavier Claessens <xavier.claessens@collabora.com>

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