Prefer to use File.binread instead of IO.binread

ext/fiddle/win32/libffi-config.rb

@@ -38,11 +38,11 @@ conf['TARGET'] = /^x64/ =~ host ? "X86_WIN64" : "X86_WIN32"
 FileUtils.mkdir_p([builddir, "#{builddir}/include", "#{builddir}/src/x86"])
 FileUtils.cp("#{basedir}/fficonfig.h", ".", preserve: true)
 
-hdr = IO.binread("#{srcdir}/include/ffi.h.in")
+hdr = File.binread("#{srcdir}/include/ffi.h.in")
 hdr.gsub!(/@(\w+)@/) {conf[$1] || $&}
 hdr.gsub!(/^(#if\s+)@\w+@/, '\10')
 IO.binwrite("#{builddir}/include/ffi.h", hdr)
 
-mk = IO.binread("#{basedir}/libffi.mk.tmpl")
+mk = File.binread("#{basedir}/libffi.mk.tmpl")
 mk.gsub!(/@(\w+)@/) {conf[$1] || $&}
 IO.binwrite("Makefile", mk)