Build libraries even if neither 'stage' nor 'install' is requested.

[SVN r28368]

Jamfile.v2

@@ -183,6 +183,10 @@ install stage : libs/$(libraries)/build
 
 explicit install install-libs install-headers stage ;        
 
+# Just build the libraries, don't install them anywhere.
+# This is what happend with just "bjam --v2".
+alias build_all : libs/$(libraries)/build ;
+
 
 # Make project ids of all libraries known.