$(INSTALL_PROG) is evaluated to libtool if using libtool, while
$(INSTALL) is not.  Use $(INSTALL_PROG) so that libtool is used
with target too when necessary.  This allows, for example, to
link qemu with shared libcacard.

Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
Cc: Fam Zheng <famz@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Alon Levy <alevy@redhat.com>
Cc: qemu-trivial@nongnu.org
--
This is done on top of previous patch (using $(STRIP)), but it can
be used by its own.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>