fix: avoid buildStart hook for formatter resolution

This hook is extremely unreliable and may be called several times at
once, so it's best to avoid it and instead completely move formatter
resolution to the transform hook, even though that doesn't make sense
concern-wise.

src/plugin/plugin.ts

@@ -1,6 +1,6 @@
 import { dataToEsm } from '@rollup/pluginutils'
 import type { CompileFn } from '@formatjs/cli-lib'
-import { createUnplugin, type RollupPlugin } from 'unplugin'
+import { createUnplugin } from 'unplugin'
 import { basePluginName } from '../shared/consts.ts'
 import {
   createOptionsResolver,
@@ -75,53 +75,13 @@ export const plugin = createUnplugin<Options_, false>((options_, meta) => {
     compileFunc = await getBultinFormatter(format)
   }
 
-  /** @see https://github.com/unjs/unplugin/issues/293 */
-  const buildStart = (() => {
-    let buildStartCall: Promise<void> | undefined
-
-    function buildStart() {
-      if (buildStartCall != null) {
-        throw new BaseError('buildStart() has already been called')
-      }
-
-      return (buildStartCall = (async () => {
-        try {
-          return await resolveFormatter()
-        } finally {
-          buildStartCall = undefined
-        }
-      })())
-    }
-
-    return {
-      run: buildStart,
-      async waitForCompletion() {
-        await buildStartCall
-      },
-    }
-  })()
-
   return {
     name: basePluginName,
 
     rollup: {
       ...(pluginsWrapping.use &&
         meta.framework === 'rollup' &&
-        (() => {
-          // unplugin doesn't have hook merging, so this is the way to go
-          const { buildStart: pluginsWrap } = rollupWrappingPartial(
-            pluginsWrapping,
-            filter,
-          )
-
-          return {
-            async buildStart(rollupOptions) {
-              await buildStart.run()
-
-              pluginsWrap?.call(this, rollupOptions)
-            },
-          } satisfies Omit<RollupPlugin, 'name'>
-        })()),
+        rollupWrappingPartial(pluginsWrapping, filter)),
       api,
     },
 
@@ -143,18 +103,13 @@ export const plugin = createUnplugin<Options_, false>((options_, meta) => {
       return filter(id)
     },
 
-    buildStart: buildStart.run,
-
     async transform(code, id) {
-      try {
-        await buildStart.waitForCompletion()
-      } catch (err) {
-        this.error(
-          new BaseError('Previously invoked buildStart() failed', {
-            cause: err,
-          }),
-        )
-        return
+      if (compileFunc == null) {
+        try {
+          await resolveFormatter()
+        } catch (err) {
+          this.error(err)
+        }
       }
 
       if (compileFunc == null) {