evil: make it possible to build the library alone.

evil: make it possible to build the library alone.

So I have been battling with autotools on this for a full week now,
and what we want is basically impossible. A.k.a. one file definition
and possibility to do a full build or just a partial build of efl.
Even moving to just partial build require to land a massive patch that
change everything in our build system and this is just not a road I
want to take.

For reference, if one day automake allow the use of any kind of variable
(autoconf AC_SUBST expansion or $()) in the _SOURCES parameter, it will
be possible to fix. Alternatively if they allow to build subdirectory
before they do BUILT_SOURCE, it would make it possible to incrementaly
move to only partial build. In the mean time, a less problematic solution
is to duplicate source code.