Linux 2.6 nanosecond time stamp weirdness breaks GCC build

[Joe Buck]

[ Linux 2.6 losing the nanoseconds from a file timestamp ]

There are two different failure modes, but in most cases only one
results in a real problem.

Case 1: make falsely thinks that the .o is younger than the .c.  It
decides not to rebuild the .o, resulting in a bad build.

Case 2: make falsely thinks that the .c is younger than the .o.  It
recompiles the .c file, even though it didn't have to.  Harmless.

So if we can make the bad situation look like a tie, and always rebuild
in the case of a tie, we will obtain valid builds, sometimes with
an extra compilation or two.