BuildSystem: Sort input file lists

so that godot package builds reproducibly
in spite of indeterministic filesystem readdir order
and http://bugs.python.org/issue30461

See https://reproducible-builds.org/ for why this is good.

Sort font input file list, so that builtin_fonts.gen.h
is created in a reproducible way

Sort list of platforms, so that editor/register_exporters.gen.cpp
is created in a reproducible way

Sort list of source files, so that .a files and resulting godot binaries
are created in a reproducible way

editor/SCsub

@@ -77,6 +77,7 @@ if env['tools']:
     # Fonts
     flist = glob.glob(path + "/../thirdparty/fonts/*.ttf")
     flist.extend(glob.glob(path + "/../thirdparty/fonts/*.otf"))
+    flist.sort()
     env.Depends('#editor/builtin_fonts.gen.h', flist)
     env.CommandNoCache('#editor/builtin_fonts.gen.h', flist, run_in_subprocess(editor_builders.make_fonts_header))