chore: optimize termux_step_get_dependencies

[twaik]

Removed external commands invocations where possible.
United some conditions under single test invocation
Refactored termux_extract_dep_info to avoid re-sourcing build.sh.
Modified package extraction sequence to avoid storage hit and avoid spawning two more commands for checking if in-tar files are prefixed with ./ or not.

With these changes termux_step_dependencies execution time drops from 12s to 7s during kf6-breeze-icons rebuilding.

Also it reduces ~0.1s-~2.0s per package during archive extracting step (depends on package size), which is good for packages with lots of dependencies (like kf6-breeze-icons).

[robertkirkman]

I tested it, I can confirm this is faster. I thought that termux_step_get_dependencies() was pretty fast already, but this change can add up to a significant benefit since it runs a lot.

[twaik]

This change makes it faster mostly for package rebuilding since I modified only this codepath.
But probably we can make regular building with dependency downloading much faster by parallelizing package downloads. I can take a look at this later. But after merging this PR.

[twaik]

Well, seems like [[ is faster than [. Pure miracle.
... But not much.

$ time for ((i=0; i<1000000; i++)); do :; done
real    0m1.017s
user    0m1.017s
sys     0m0.000s

$ time for ((i=0; i<1000000; i++)); do [ -f /dev/null ]; done
real    0m1.949s
user    0m1.629s
sys     0m0.319s

$ time for ((i=0; i<1000000; i++)); do [[ -f /dev/null ]]; done
real    0m1.389s
user    0m1.075s
sys     0m0.314s

[twaik]

Also I placed post-timestamp-creation sleep with check if it is needed or 1 second already passed. Should reduce building of each package by 1 second.

I checked all packages overriding termux_step_get_source and no one of them installs files directly to $TERMUX_PREFIX so it should be fine.

[twaik]

I will merge this in 24 hours if nobody minds or after it gets 2+ more approves.

[twaik]

Ok, I'll merge it in 20 hours if nobody minds or after it gets 2+ more approves.

[TomJo2000]

Forgot to approve this earlier.
Go ahead.

[Maxython]

Ok, I'll merge it in 20 hours if nobody minds or after it gets 2+ more approves.

Wait, let me test how this all works with termux-pacman repos.