PNPM_HOME_PATH=>PNPM_HOME

This change is needed to make the action compatible with pnpm v7.

Related breaking change in pnpm: pnpm/pnpm#4280

src/install-pnpm/run.ts

@@ -23,16 +23,16 @@ export async function runSelfInstaller(inputs: Inputs): Promise<number> {
   const response = await fetch('https://pnpm.js.org/pnpm.js')
   response.body.pipe(cp.stdin)
 
-  const result = await new Promise<number>((resolve, reject) => {
+  const exitCode = await new Promise<number>((resolve, reject) => {
     cp.on('error', reject)
     cp.on('close', resolve)
   })
-  if (result === 0) {
+  if (exitCode === 0) {
     const pnpmHome = join(dest, 'node_modules/.bin')
     core.addPath(pnpmHome)
-    core.exportVariable('PNPM_HOME_PATH', pnpmHome)
+    core.exportVariable('PNPM_HOME', pnpmHome)
   }
-  return result
+  return exitCode
 }
 
 export default runSelfInstaller