Fix run-tests.php --file-cache-prime with multiple workers

We want to remove the directory only before running tests, rather than for every
test. That causes races, but also defeats the purpose of priming the cache.

Author: iluuu1994

run-tests.php

@@ -700,6 +700,12 @@ function main(): void
     verify_config($php);
     write_information($user_tests, $phpdbg);
 
+    if ($file_cache === 'prime') {
+        $cache_dir = get_file_cache_dir();
+        rmdir_recursive($cache_dir);
+        mkdir($cache_dir, recursive: true);
+    }
+
     if ($test_cnt) {
         $exts_tested = [];
         $exts_skipped = [];
@@ -1054,6 +1060,11 @@ function find_files(string $dir, bool $is_ext_dir = false, bool $ignore = false)
     closedir($o);
 }
 
+function get_file_cache_dir(): string
+{
+    return sys_get_temp_dir() . DIRECTORY_SEPARATOR . 'php-run-tests-file-cache';
+}
+
 function rmdir_recursive($dir)
 {
     if (!file_exists($dir)) {
@@ -2091,11 +2102,7 @@ function run_test(string $php, $file, array $env): string
     $orig_ini_settings = settings2params($ini_settings);
 
     if ($file_cache !== null) {
-        $ini_settings['opcache.file_cache'] = sys_get_temp_dir() . DIRECTORY_SEPARATOR . 'php-run-tests-file-cache';
-        if ($file_cache === 'prime') {
-            rmdir_recursive($ini_settings['opcache.file_cache']);
-            mkdir($ini_settings['opcache.file_cache'], recursive: true);
-        }
+        $ini_settings['opcache.file_cache'] = get_file_cache_dir();
         // Make sure warnings still show up on the second run.
         $ini_settings['opcache.record_warnings'] = '1';
         // File cache is currently incompatible with JIT.