Tell stacker about the correct initial stack size

[saethlin]

I've been debugging #138889, and I think this is a fix.

Android is not supported by stacker. So it ends up in the fallback case, where stacker cannot determine what the initial stack size is. So the first call to stacker::maybe_grow allocates a stack of the passed-in size. On Android, this would immediately shrink the initial stack size from 8 MB from 1 MB, and then we blow the (now much smaller) stack with recursive calls.

I think the problem in the compiler is that we should never pass stacker::maybe_grow a stack size that is smaller than the current stack, so I've moved code around so that the STACK_SIZE static that we set when the compiler is initialized in rustc_interface can be shared by rustc_data_structures.

---

I think the cfg(aix) was added in #131116 to fix the same problem, so it shouldn't be required anymore. target_os = "aix" is also unsupported by stacker.

[saethlin]

@bors try @rust-timer queue

[rust-bors]

☀️ Try build successful (CI)
Build commit: 6a21530 (6a2153010d3bb280dd46ae569f940c656b18d2f3)
Base parent: c397dae (c397dae808f70caebab1fc4e11b3edf7e59f58c7)

[rust-timer]

Finished benchmarking commit (6a21530): comparison URL.

Overall result: ❌ regressions - please read:

Benchmarking means the PR may be perf-sensitive. It's automatically marked not fit for rolling up. Overriding is possible but disadvised: it risks changing compiler perf.

Next, please: If you can, justify the regressions found in this try perf run in writing along with @rustbot label: +perf-regression-triaged. If not, fix the regressions and do another perf run. Neutral or positive results will clear the label automatically.

@bors rollup=never
@rustbot label: -S-waiting-on-perf +perf-regression

Instruction count

Our most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.

	mean	range	count
Regressions ❌ (primary)	0.3%	[0.2%, 0.4%]	8
Regressions ❌ (secondary)	0.4%	[0.2%, 0.6%]	34
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.3%	[0.2%, 0.4%]	8

Max RSS (memory usage)

This perf run didn't have relevant results for this metric.

Cycles

Results (primary 3.2%, secondary -1.0%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	3.2%	[2.4%, 4.4%]	3
Regressions ❌ (secondary)	3.3%	[3.0%, 3.5%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-3.9%	[-6.0%, -2.7%]	3
All ❌✅ (primary)	3.2%	[2.4%, 4.4%]	3

Binary size

This perf run didn't have relevant results for this metric.

Bootstrap: 485.944s -> 486.323s (0.08%)
Artifact size: 393.37 MiB -> 393.30 MiB (-0.02%)