https://github.com/sass/sassc-ruby/pull/178

commit 0458396c8494aff3d71aa75cb401b2ad6fe78c1e
Author: Bernhard M. Wiedemann <bwiedemann@suse.de>
Date:   Thu Jan 9 21:12:33 2020 +0100

    Sort input file list
    
    so that libsass.so builds in a reproducible way
    in spite of indeterministic filesystem readdir order.
    
    See https://reproducible-builds.org/ for why this is good.
    
    This PR was done while working on reproducible builds for openSUSE.

diff --git a/ext/extconf.rb b/ext/extconf.rb
index 08e067c..5e36d97 100644
--- a/ext/extconf.rb
+++ b/ext/extconf.rb
@@ -56,7 +56,7 @@ $INCFLAGS << " -I$(srcdir)/libsass/include"
 $VPATH << "$(srcdir)/libsass/src"
 Dir.chdir(__dir__) do
   $VPATH += Dir['libsass/src/*/'].map { |p| "$(srcdir)/#{p}" }
-  $srcs = Dir['libsass/src/**/*.{c,cpp}']
+  $srcs = Dir['libsass/src/**/*.{c,cpp}'].sort
 end
 
 MakeMakefile::LINK_SO << "\nstrip -x $@"