remove libdl

Index: meson.build
--- meson.build.orig
+++ meson.build
@@ -23,7 +23,6 @@ if extras_path != ''
 endif
 
 m_dep = cpp.find_library('m', required : false)
-dl_dep = cpp.find_library('dl')
 libjpeg_dep = dependency('libjpeg')
 libpng_dep = dependency('libpng')