[libjava] Cleanup automake conditionals (part 2)

[Tom Tromey]

>>>>> "KC" == Kelley Cook <kcook@gcc.gnu.org> writes:

KC> For all the conditional sources for libgcj, we were defining a new
KC> variable with either an additional sourcefile or a null string when we
KC> could have just appended the additional sources to libgcj_la_SOURCES,
KC> which makes it clearer to see the intended build logic.

KC> OK?

Yes, thanks.  I suspect this use of conditionals predates the ability
to '+=' conditionally in automake.

Tom