Allow build/gen_stub.php to process multiple CLI file args (php#7179)

E.g. `build/gen_stub.php *.stub.php` will generate `*_arginfo.h`
from multiple files.

Previously, gen_stub.php would silently ignore files after the first file.

Invoking gen_stub.php with no arguments will continue to process the entire
directory.

Author: TysonAndre

build/gen_stub.php

@@ -2311,18 +2311,20 @@ function initPhpParser() {
 }
 
 $fileInfos = [];
-$location = $argv[$optind] ?? ".";
-if (is_file($location)) {
-    // Generate single file.
-    $fileInfo = processStubFile($location, $context);
-    if ($fileInfo) {
-        $fileInfos[] = $fileInfo;
-    }
-} else if (is_dir($location)) {
-    $fileInfos = processDirectory($location, $context);
-} else {
-    echo "$location is neither a file nor a directory.\n";
-    exit(1);
+$locations = array_slice($argv, $optind) ?: ['.'];
+foreach (array_unique($locations) as $location) {
+    if (is_file($location)) {
+        // Generate single file.
+        $fileInfo = processStubFile($location, $context);
+        if ($fileInfo) {
+            $fileInfos[] = $fileInfo;
+        }
+    } else if (is_dir($location)) {
+        array_push($fileInfos, ...processDirectory($location, $context));
+    } else {
+        echo "$location is neither a file nor a directory.\n";
+        exit(1);
+    }
 }
 
 if ($printParameterStats) {