build-sys: use proper dependencies on libproc.la

Use LDADD or *_LDADD instead of AM_LDFLAGS to refer to libproc.la.

This is recommended in the automake manual: http://www.gnu.org/software/automake/manual/html_node/Linking.html

Before this commit, parallel builds may break, as there is no explicit dependency to ensure the library is built before the binaries that try to link to it.

Tested by running make -jNN repeatedly for different levels of parallelism to ensure the build works. Also checked that make check and make distcheck still work as expected. Also made sure that a parallel make invocation works with make -j distcheck.

Reported-by: Jim Warner james.warner@comcast.net

Signed-off-by: Filipe Brandenburger filbranden@google.com