[gtk+/gtk-3-22] Adwaita/README: Update to reflect we use sassc now

[Daniel Boles <dboles src gnome org>]

commit 4515c727068e0854e6d5594da47949a4a96f13bf
Author: Daniel Boles <dboles src gnome org>
Date:   Sun Oct 8 13:59:30 2017 +0100

    Adwaita/README: Update to reflect we use sassc now
    
    We moved from the Ruby compiler to sassc in
    commit 67953e9cfb5dec4a509525fd572c3d21c38d8cff, so this copies across
    the updated info about building from GTK+ 4.
    
    Also, explain the purpose of parse-sass.sh, since while that is not
    mentioned in GTK+ 4 – and perhaps does not need to be, thanks to Meson –
    we are still on Autotools here, and rebuilding the entirety of GTK+ 3 if
    you only edited the CSS is a lot of waiting for no good reason.

 gtk/theme/Adwaita/README |   17 ++++++++---------
 1 files changed, 8 insertions(+), 9 deletions(-)
---
diff --git a/gtk/theme/Adwaita/README b/gtk/theme/Adwaita/README
index b5a397e..0fbb589 100644
--- a/gtk/theme/Adwaita/README
+++ b/gtk/theme/Adwaita/README
@@ -1,11 +1,11 @@
 Summary
 -------
 
-* Do not edit the CSS directly, edit the source SCSS files and process them with SASS (run 
-  `./parse-sass.sh` when you have the required software installed, as described below)
-* To be able to use the latest/adequate version of sass, install ruby, gem, sass & bundle.
-  On Fedora F20, this is done with `sudo dnf install rubygems && gem install bundle && bundle install`
-  from the same directory this README resides in.
+* Do not edit the CSS directly, edit the source SCSS files
+* To be able to use the latest/adequate version of SASS, install sassc
+* The configure script will detect whether or not you have sassc installed;
+  if you do, it will regenerate the CSS every time you modify the SCSS files
+  and rebuild GTK+. To rebuild the CSS only, run the script ./parse-sass.sh
 
 How to tweak the theme
 ----------------------
@@ -30,7 +30,6 @@ _drawing.scss       - drawing helper mixings/functions to allow easier definitio
 _common.scss        - actual definitions of style for each widget. This is where you are likely to add/remove
                       your changes.
                       
-You can read about SASS at http://sass-lang.com/documentation/. Once you make your changes to the
-_common.scss file, you can either run the ./parse-sass.sh script or keep SASS watching for changes as you
-edit. This is done by running `bundle exec sass --watch --sourcemap=none .` If sass is out of date, or is
-missing, you can install it with `bundle install`.
+You can read about SASS at http://sass-lang.com/documentation/. Once you make
+your changes to the _common.scss file, GTK+ will rebuild the CSS files. If you
+want to build only the CSS files, not all of GTK+, simply run ./parse-sass.sh