Updated build instructions

README.md

@@ -10,13 +10,28 @@ providing Qt, GTK and ncurses frontends. Originally it was developed for
 
 This part contains the Qt graphical frontend.
 
+
 ### Building
 
-Libyui uses CMake, driven by a slightly complex set of
-[CMakefiles](https://github.com/libyui/libyui/tree/master/buildtools). For
-reproducible builds it is best to use the [libyui-rake](
-https://github.com/libyui/libyui-rake) Ruby gem like the [Jenkins CI](
-https://ci.opensuse.org/view/libyui/) jobs do.
+Libyui uses CMake. Most operations are available from the toplevel
+_Makefile.repo_:
+
+```
+make -f Makefile.repo
+cd build
+make
+```
+
+or
+
+```
+make -f Makefile.repo build
+```
+
+
+For reproducible builds it is best to use the
+[libyui-rake](https://github.com/libyui/libyui-rake)
+Ruby gem like the [Jenkins CI](https://ci.opensuse.org/view/libyui/) jobs do.
 
 It can be installed from [rubygems.org](https://rubygems.org/gems/libyui-rake/)
 using this command (Ruby needs to be installed in the system):