Fix building with --as-needed LD flag

Fix building with --as-needed LD flag

When using GNU ld --as-needed option, you need to ensure that the
order of parameters to the linker is formally correct, with libraries
coming after the object files. For this reason, don't use LDFLAGS for
passing the libraries, and make sure that LDLIBS goes at the end of
the line.

Signed-off-by: Diego E. 'Flameeyes' Pettenò <flameeyes@gmail.com>
Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>