The race detector can't handle ASLR (adddress space layout randomization).
On some platforms it can re-exec the binary with ASLR off. But not NetBSD.
For NetBSD we have to introduce a special ELF header note that tells
the kernel not to use ASLR.
This works fine for internal linking. For external linking it also works,
but "readelf -n" shows multiple notes in the resulting binary. Maybe the
last one wins? Not sure, but it appears to work.