perf: use availableParallelism instead of exec (#123)

* fix: use `availableParallelism` instead of `exec`

* test: remove unused test

* test: fix failing cpu test

---------

Co-authored-by: Vladimir Sheremet <[email protected]>

Author: AriPerkkio

src/index.ts

@@ -11,7 +11,7 @@ import { inspect, types } from 'node:util'
 import assert from 'node:assert'
 import { performance } from 'node:perf_hooks'
 import { readFileSync } from 'node:fs'
-import { amount as physicalCpuCount } from './physicalCpuCount'
+import { availableParallelism } from 'node:os'
 import {
   type ReadyMessage,
   type RequestMessage,
@@ -50,7 +50,7 @@ declare global {
   }
 }
 
-const cpuCount: number = physicalCpuCount
+const cpuCount: number = availableParallelism()
 
 interface AbortSignalEventTargetAddOptions {
   once: boolean

src/physicalCpuCount.ts

@@ -51,7 +51,7 @@ vi.mock(import('node:os'), async (importOriginal) => {
   const original = await importOriginal()
   return {
     ...original,
-    default: { ...original.default, cpus: () => Array(cpuCount) },
+    availableParallelism: () => cpuCount,
   }
 })