Audit CMake linking flags

If you look at the linking flags for autoconf's stout tests build:

```
./.libs/libgmock.a glog-0.3.3/.libs/libglog.a -lgflags protobuf-2.5.0/src/.libs/libprotobuf.a -lpthread -ldl -lz /usr/lib/x86_64-linux-gnu/libcurl-nss.so /usr/lib/x86_64-linux-gnu/libsvn_delta-1.so /usr/lib/x86_64-linux-gnu/libsvn_subr-1.so /usr/lib/x86_64-linux-gnu/libapr-1.so -lrt -pthread
```

you'll notice that they are much more concise than our CMake build:

```
-L/usr/lib/x86_64-linux-gnu/libapr-1.so -L/usr/lib/x86_64-linux-gnu/libsvn_client-1.so -L/usr/lib/x86_64-linux-gnu/libsvn_delta-1.so -L/usr/lib/x86_64-linux-gnu/libsvn_diff-1.so -L/usr/lib/x86_64-linux-gnu/libsvn_fs-1.so -L/usr/lib/x86_64-linux-gnu/libsvn_fs_fs-1.a -L/usr/lib/x86_64-linux-gnu/libsvn_fs_util-1.a -L/usr/lib/x86_64-linux-gnu/libsvn_ra-1.so -L/usr/lib/x86_64-linux-gnu/libsvn_ra_local-1.a -L/usr/lib/x86_64-linux-gnu/libsvn_ra_serf-1.a -L/usr/lib/x86_64-linux-gnu/libsvn_ra_svn-1.a -L/usr/lib/x86_64-linux-gnu/libsvn_repos-1.so -L/usr/lib/x86_64-linux-gnu/libsvn_subr-1.so -L/usr/lib/x86_64-linux-gnu/libsvn_wc-1.so -L/home/joris/projects/mesos/build/3rdparty/libprocess/3rdparty/gmock-1.7.0/src/gmock-1.7.0-lib/lib -L/home/joris/projects/mesos/build/3rdparty/libprocess/3rdparty/gmock-1.7.0/src/gmock-1.7.0-build/gtest/lib/.libs -L/home/joris/projects/mesos/build/3rdparty/libprocess/3rdparty/glog-0.3.3/src/glog-0.3.3-lib/lib/lib -L/home/joris/projects/mesos/build/3rdparty/libprocess/3rdparty/protobuf-2.5.0/src/protobuf-2.5.0-lib/lib/lib -rdynamic -lpthread -lgmock -lsvn_client-1 -lsvn_delta-1 -lsvn_diff-1 -lsvn_fs-1 -Wl,-Bstatic -lsvn_fs_fs-1 -lsvn_fs_util-1 -Wl,-Bdynamic -lsvn_ra-1 -Wl,-Bstatic -lsvn_ra_local-1 -lsvn_ra_serf-1 -lsvn_ra_svn-1 -Wl,-Bdynamic -lsvn_repos-1 -lsvn_subr-1 -lsvn_wc-1 -lglog -lprotobuf -lgtest -ldl -lapr-1 -lrt -Wl,-rpath,/usr/lib/x86_64-linux-gnu/libapr-1.so:/usr/lib/x86_64-linux-gnu/libsvn_client-1.so:/usr/lib/x86_64-linux-gnu/libsvn_delta-1.so:/usr/lib/x86_64-linux-gnu/libsvn_diff-1.so:/usr/lib/x86_64-linux-gnu/libsvn_fs-1.so:/usr/lib/x86_64-linux-gnu/libsvn_fs_fs-1.a:/usr/lib/x86_64-linux-gnu/libsvn_fs_util-1.a:/usr/lib/x86_64-linux-gnu/libsvn_ra-1.so:/usr/lib/x86_64-linux-gnu/libsvn_ra_local-1.a:/usr/lib/x86_64-linux-gnu/libsvn_ra_serf-1.a:/usr/lib/x86_64-linux-gnu/libsvn_ra_svn-1.a:/usr/lib/x86_64-linux-gnu/libsvn_repos-1.so:/usr/lib/x86_64-linux-gnu/libsvn_subr-1.so:/usr/lib/x86_64-linux-gnu/libsvn_wc-1.so:/home/joris/projects/mesos/build/3rdparty/libprocess/3rdparty/gmock-1.7.0/src/gmock-1.7.0-lib/lib:/home/joris/projects/mesos/build/3rdparty/libprocess/3rdparty/gmock-1.7.0/src/gmock-1.7.0-build/gtest/lib/.libs:/home/joris/projects/mesos/build/3rdparty/libprocess/3rdparty/glog-0.3.3/src/glog-0.3.3-lib/lib/lib:/home/joris/projects/mesos/build/3rdparty/libprocess/3rdparty/protobuf-2.5.0/src/protobuf-2.5.0-lib/lib/lib
```

We need to (1) audit this so that we are confident the linking process works like we want it to, and (2) make sure we don't triple link dependencies.