Improve diagnostic on PCRE JIT mmap failure

Print a more informative message that indicates that this is
likely a permission issue, and also indicate that pcre.jit=0
can be used to work around it.

Also automatically disable the JIT, so that this message is
only shown once.

See bug #78630.

Author: nikic

ext/pcre/php_pcre.c

@@ -783,6 +783,12 @@ PHPAPI pcre_cache_entry* pcre_get_compiled_regex_cache(zend_string *regex)
 			if (!pcre2_pattern_info(re, PCRE2_INFO_JITSIZE, &jit_size) && jit_size > 0) {
 				poptions |= PREG_JIT;
 			}
+		} else if (rc == PCRE2_ERROR_NOMEMORY) {
+			php_error_docref(NULL, E_WARNING,
+				"Allocation of JIT memory failed, PCRE JIT will be disabled. "
+				"This is likely caused by security restrictions. "
+				"Either grant PHP permission to allocate executable memory, or set pcre.jit=0");
+			PCRE_G(jit) = 0;
 		} else {
 			pcre2_get_error_message(rc, error, sizeof(error));
 			php_error_docref(NULL, E_WARNING, "JIT compilation failed: %s", error);