Test for pcntl availability from the command line, not Apache

Summary:
In RHEL6 at the least, pcntl installs from distro package management to the CLI
but not to Apache. Since we don't need it in apache and it's a pain to build
manually, just verify it exists on the CLI.

Test Plan:
Simulated script failures and verified setup output.

Reviewed By: codeblock
Reviewers: codeblock, aran, jungejason, tuomaspelkonen
CC: aran, epriestley, kevinwallace, codeblock
Differential Revision: 380

scripts/setup/pcntl_available.php

@@ -0,0 +1,24 @@
+#!/usr/bin/env php
+<?php
+
+/*
+ * Copyright 2011 Facebook, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+if (extension_loaded('pcntl')) {
+  echo "YES\n";
+} else {
+  echo "NO\n";
+}

src/infrastructure/setup/PhabricatorSetup.php

@@ -36,7 +36,6 @@ class PhabricatorSetup {
       'mysql',
       'hash',
       'json',
-      'pcntl',
       'openssl',
     );
     foreach ($extensions as $extension) {
@@ -47,10 +46,32 @@ class PhabricatorSetup {
         return;
       }
     }
+
+    $root = dirname(phutil_get_library_root('phabricator'));
+
+    // On RHEL6, doing a distro install of pcntl makes it available from the
+    // CLI binary but not from the Apache module. This isn't entirely
+    // unreasonable and we don't need it from Apache, so do an explicit test
+    // for CLI availability.
+    list($err, $stdout, $stderr) = exec_manual(
+      '%s/scripts/setup/pcntl_available.php',
+      $root);
+    if ($err) {
+      self::writeFailure();
+      self::write("Unable to execute scripts/setup/pcntl_available.php.");
+      return;
+    } else {
+      if (trim($stdout) == 'YES') {
+        self::write(" okay  pcntl is available from the command line.\n");
         self::write("[OKAY] All extensions OKAY\n\n");
+      } else {
+        self::write(" warn  pcntl is not available!\n");
+        self::write("[WARN] *** WARNING *** pcntl extension not available. ".
+                    "You will not be able to run daemons.\n");
+      }
+    }
 
     self::writeHeader("GIT SUBMODULES");
-    $root = dirname(phutil_get_library_root('phabricator'));
     if (!Filesystem::pathExists($root.'/.git')) {
       self::write(" skip  Not a git clone.\n\n");
     } else {