Print selected configure flags in install plan.
When debugging #3827, I wished I could see what the profiling status of all packages in our install plan was. This patch outputs this information, by printing the *configure flag* we would have passed to configure. In an ideal world, we'd print exactly the configure flags we actually pass in practice. But this is not so great because the flag lists tend to be really long. So we pare it down in the following ways: 1. Not all flags are output: only a selected few. In this patch, it's just enabling/disabling profiling flags, but we could add more. 2. If we have Flag False for profiling, we will actually explicitly pass --disable-profiling to the configure script. But it's not so good to output that to the user. So 'nubFlag' lets us drop the flag, if omitting it would have the same effect as specifying it. Figuring that out is a little tricky though. Signed-off-by: Edward Z. Yang <email@example.com>