android: use posix_memalign for aligned allocations

[RalfJung]

Our target page says

Rust will support the most recent Long Term Support (LTS) Android Native Development Kit (NDK). By default Rust will support all API levels supported by the NDK, but a higher minimum API level may be required if deemed necessary.

According to this, the minimum API level of the current LTS NDK is 21. According to this, posix_memalign exists since API level 16. So I think we should be able to use it here?

[rustbot]

r? @cuviper

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[workingjubilee]

@RalfJung this is waiting on #120593

[workingjubilee]

...wait, I'm an idiot, 19 is higher than 16.

[workingjubilee]

Yeah, that's correct.

@bors r+

[bors]

📌 Commit dde1134 has been approved by workingjubilee

It is now in the queue for this repository.

[bors]

⌛ Testing commit dde1134 with merge cf2baaa...

[bors]

☀️ Test successful - checks-actions
Approved by: workingjubilee
Pushing cf2baaa to master...

[rust-timer]

Finished benchmarking commit (cf2baaa): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

This benchmark run did not return any relevant results for this metric.

Max RSS (memory usage)

Results (primary 3.9%)

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	3.9%	[3.9%, 3.9%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	3.9%	[3.9%, 3.9%]	1

Cycles

This benchmark run did not return any relevant results for this metric.

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 669.005s -> 671.867s (0.43%)
Artifact size: 316.23 MiB -> 316.05 MiB (-0.06%)