lang/ruby31: Add upstream patch to fix bug of mkmf library

There is bug in mkmf library of Ruby 3.1 that it fails to detect
pkg-config command if it isn't installed in environment that Ruby is
built, and it causes build error of some ports when default version of
Ruby is 3.1. So add upstream patch to fix it.

Reference:	https://bugs.ruby-lang.org/issues/19189
PR:		269197
Approved by:	maintainer timeout
MFH:		2023Q1

Mk/Uses/ruby.mk

@@ -162,7 +162,7 @@ RUBY_PORTREVISION=	0
 # Ruby 3.1
 #
 RUBY_DISTVERSION=	3.1.3
-RUBY_PORTREVISION=	0
+RUBY_PORTREVISION=	1
 
 .      elif ${RUBY_VER} == 3.2
 #

lang/ruby31/files/patch-mkmf-pkg-config

@@ -0,0 +1,25 @@
+From 613fca01486e47dee9364a2fd86b5f5e77fe23c8 Mon Sep 17 00:00:00 2001
+From: Nobuyoshi Nakada <nobu@ruby-lang.org>
+Date: Wed, 7 Dec 2022 22:14:44 +0900
+Subject: [PATCH] [Bug #19189] Fallback to the default "pkg-config"
+
+---
+ lib/mkmf.rb | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git lib/mkmf.rb lib/mkmf.rb
+index e94733c635..0fbc1cc2e5 100644
+--- lib/mkmf.rb
++++ lib/mkmf.rb
+@@ -1866,7 +1866,7 @@ def pkg_config(pkg, *options)
+     if pkgconfig = with_config("#{pkg}-config") and find_executable0(pkgconfig)
+       # if and only if package specific config command is given
+     elsif ($PKGCONFIG ||=
+-           (pkgconfig = with_config("pkg-config", RbConfig::CONFIG["PKG_CONFIG"])) &&
++           (pkgconfig = with_config("pkg-config") {config_string("PKG_CONFIG") || "pkg-config"}) &&
+            find_executable0(pkgconfig) && pkgconfig) and
+         xsystem([*envs, $PKGCONFIG, "--exists", pkg])
+       # default to pkg-config command
+-- 
+2.39.1
+