Restore npm SIGINT behavior (reverts #41)

This reverts the behavioral change from #41.

This change caused pnpm to improperly handle interactive
shell Ctrl-C, trapping the received signal and also ignoring
the abnormal exit of the script. This often results still
in a quick exit (because the script has terminated), but
with exit code 0.

PR #41 resulted in incorrect behavior, which also diverges
from npm (as well as `node --run`). As another problem, it
made pnpm internally inconsistent as Ctrl-C results in non-zero
in situations when lifecycles scripts are not actively running.
Even in the context of pnpm run, a very quick Ctrl-C, prior to
spawn, results in a non-zero pnpm exit.

For additional discussion see: #51

Fixes: pnpm/pnpm#9626

Author: isaacl

index.js

@@ -281,7 +281,7 @@ function runCmd_ (cmd, pkg, env, wd, opts, stage, unsafe, uid, gid, cb_) {
   proc.on('close', (code, signal) => {
     opts.log.silly('lifecycle', logid(pkg, stage), 'Returned: code:', code, ' signal:', signal)
     let err
-    if (signal && signal !== 'SIGINT') {
+    if (signal) {
       err = new PnpmError('CHILD_PROCESS_FAILED', `Command failed with signal "${signal}"`)
       process.kill(process.pid, signal)
     } else if (code) {

test/index.js

@@ -205,7 +205,7 @@ test('throw error signal kills child', async function (t) {
   stubProcessExit.restore()
 })
 
-test('no error on INT signal from child', async function (t) {
+test('exit with error on INT signal from child', async function (t) {
   if (isWindows()) {
     // On Windows there is no way to get the INT signal
     return
@@ -233,7 +233,7 @@ test('no error on INT signal from child', async function (t) {
   const dir = fixture
   const pkg = require(path.join(fixture, 'package.json'))
 
-  await t.resolves(async () => {
+  await t.rejects(async () => {
     await lifecycle(pkg, 'signal-int', fixture, {
       stdio: 'pipe',
       log,
@@ -243,14 +243,15 @@ test('no error on INT signal from child', async function (t) {
   })
 
   stubProcessExit.restore()
+  stubProcessExit.calledOnceWith(process.pid, 'SIGINT')
 
   t.ok(
-    !info.calledWithMatch(
+    info.calledWithMatch(
       'lifecycle',
       'undefined~signal-int:',
       'Failed to exec signal-int script'
     ),
-    'INT signal intercepted incorrectly'
+    'INT signal not intercepted'
   )
 
   t.ok(