test/ec: build the libs only when 'make check'

test/ec: build the libs only when 'make check'

Currently, we are always building the erasure code libraries while we
need them only when 'make check' is run. Moving the test libraries to
check_LTLIBRARIES should fix this for us.

We no longer need to remove the libec libs manually, remove the lines
that do that.

Signed-off-by: Boris Ranto <branto@redhat.com>
(cherry picked from commit 0bbfea5cf13c138bbb2f0993607fa0dbf756281b)