$NetBSD: patch-meson.build,v 1.1 2023/07/25 09:07:34 abs Exp $

meson.build: fix build and avoid sigsegv

https://github.com/glmark2/glmark2/commit/7d4c4da5d34e2e70a285c345c979e5e3c1eb2c3a

--- meson.build.orig	2023-01-19 11:02:15.000000000 +0000
+++ meson.build
@@ -23,7 +23,8 @@ if extras_path != ''
 endif
 
 m_dep = cpp.find_library('m', required : false)
-dl_dep = cpp.find_library('dl')
+dl_dep = cpp.find_library('dl', required : false)
+thread_dep = dependency('threads')
 libjpeg_dep = dependency('libjpeg')
 libpng_dep = dependency('libpng')