all: test failures with `EBADF` from fork/exec on NetBSD

[gopherbot]

#!watchflakes
post <- goos == "netbsd" && (log ~ `fork/exec .*: bad file descriptor` || `fork/exec .*: bad file descriptor`)

Issue created automatically to collect these failures.

Example (log):

fork/exec /var/gobuilder/buildlet/tmp/go-build1315313087/b144/syntax.test: bad file descriptor

— watchflakes