Fix PCRE2 do not allocate JIT stack if unavailable (#13100)

spec/std/regex_spec.cr

@@ -211,7 +211,9 @@ describe "Regex" do
       {% else %}
         # Can't use regex literal because the *LIMIT_DEPTH verb is not supported in libpcre (only libpcre2)
         # and thus the compiler doesn't recognize it.
-        str.matches?(Regex.new("(*LIMIT_DEPTH=8192)^(?:[A-Za-z0-9+/]{4})*(?:[A-Za-z0-9+/]{2}==|[A-Za-z0-9+/]{3}=)?$"))
+        regex = Regex.new("(*LIMIT_DEPTH=8192)^(?:[A-Za-z0-9+/]{4})*(?:[A-Za-z0-9+/]{2}==|[A-Za-z0-9+/]{3}=)?$")
+        pending! "PCRE2 JIT mode not available." unless regex.@jit
+        str.matches?(regex)
       {% end %}
       # We don't care whether this actually matches or not, it's just to make
       # sure the engine does not stack overflow with a large string.

src/regex/pcre2.cr

@@ -4,26 +4,29 @@ require "crystal/thread_local_value"
 # :nodoc:
 module Regex::PCRE2
   @re : LibPCRE2::Code*
+  @jit : Bool
 
   # :nodoc:
   def initialize(*, _source @source : String, _options @options)
     @re = PCRE2.compile(source, pcre2_options(options) | LibPCRE2::UTF | LibPCRE2::NO_UTF_CHECK | LibPCRE2::DUPNAMES | LibPCRE2::UCP) do |error_message|
       raise ArgumentError.new(error_message)
     end
 
-    jit_compile
+    @jit = jit_compile
   end
 
-  private def jit_compile : Nil
+  private def jit_compile : Bool
     ret = LibPCRE2.jit_compile(@re, LibPCRE2::JIT_COMPLETE)
     if ret < 0
       case error = LibPCRE2::Error.new(ret)
       when .jit_badoption?
         # okay
+        return false
       else
         raise ArgumentError.new("Regex JIT compile error: #{error}")
       end
     end
+    true
   end
 
   protected def self.compile(source, options)
@@ -153,7 +156,7 @@ module Regex::PCRE2
   private def match_data(str, byte_index, options)
     match_data = LibPCRE2.match_data_create_from_pattern(@re, Regex::PCRE2.general_context)
     match_context = LibPCRE2.match_context_create(nil)
-    LibPCRE2.jit_stack_assign(match_context, nil, Regex::PCRE2.jit_stack.as(Void*))
+    LibPCRE2.jit_stack_assign(match_context, nil, Regex::PCRE2.jit_stack.as(Void*)) if @jit
     match_count = LibPCRE2.match(@re, str, str.bytesize, byte_index, pcre2_options(options) | LibPCRE2::NO_UTF_CHECK, match_data, match_context)
 
     if match_count < 0