Fix detection of PHP files to match also broken ones with leading whitespace or whitespace between shebang and <?php, refs jakzal/phpqa#336

src/Composer/Installer/BinaryInstaller.php

@@ -258,7 +258,7 @@ class BinaryInstaller
         $binContents = file_get_contents($bin);
         // For php files, we generate a PHP proxy instead of a shell one,
         // which allows calling the proxy with a custom php process
-        if (Preg::isMatch('{^(#!.*\r?\n)?<\?php}', $binContents, $match)) {
+        if (Preg::isMatch('{^(#!.*\r?\n)?[\r\n\t ]*<\?php}', $binContents, $match)) {
             // carry over the existing shebang if present, otherwise add our own
             $proxyCode = empty($match[1]) ? '#!/usr/bin/env php' : trim($match[1]);
             $binPathExported = $this->filesystem->findShortestPathCode($link, $bin, false, true);