wasmtime: enable stack probing for x86_64 targets.

[peterhuene]

This PR unconditionally enables stack probing for x86_64 targets.

On Windows, stack probing is always required because of the way Windows commits stack pages (via guard page access).

Fixes #5340.

[peterhuene]

I'll see if I can update the test not to use SIMD.

[alexcrichton]

/bench_x64

Curious!

[jlb6740]

instantiation :: cycles :: benchmarks/bz2/benchmark.wasm

No difference in performance.

[157158 193189.52 549782] commit.so
[159262 173947.68 198430] main.so

execution :: cycles :: benchmarks/bz2/benchmark.wasm

No difference in performance.

[128304680 135393814.80 220629322] commit.so
[128044472 130380997.52 132394284] main.so

compilation :: cycles :: benchmarks/bz2/benchmark.wasm

No difference in performance.

[205479004 221452290.72 251142766] commit.so
[202111130 220026159.20 254842212] main.so

instantiation :: cycles :: benchmarks/pulldown-cmark/benchmark.wasm

No difference in performance.

[186726 204750.96 228796] commit.so
[185846 205393.68 235104] main.so

compilation :: cycles :: benchmarks/spidermonkey/benchmark.wasm

No difference in performance.

[6658721004 6822664513.44 6970711408] commit.so
[6638935210 6803105818.16 6927676828] main.so

execution :: cycles :: benchmarks/spidermonkey/benchmark.wasm

No difference in performance.

[1102708506 1118591175.84 1130738536] commit.so
[1101851712 1115567785.84 1125825060] main.so

compilation :: cycles :: benchmarks/pulldown-cmark/benchmark.wasm

No difference in performance.

[297517394 323611868.32 376552374] commit.so
[292725104 324405945.28 358608704] main.so

instantiation :: cycles :: benchmarks/spidermonkey/benchmark.wasm

No difference in performance.

[487538 508903.04 619584] commit.so
[483196 508709.36 553900] main.so

execution :: cycles :: benchmarks/pulldown-cmark/benchmark.wasm

No difference in performance.

[9578432 9776958.56 10226136] commit.so
[9591706 9780255.04 9987402] main.so