FreeBSD build error: undefined: syscall.ENODATA

[rfratto]

#300 seems to have introduced a regression on FreeBSD:

vendor/github.com/prometheus/procfs/sysfs/class_thermal.go:51:22: undefined: syscall.ENODATA

You can see from the Go source that ENODATA isn't an error on FreeBSD.

Unfortunately, I don't understand this enough myself to try to contribute a fix, but this is preventing me from building node_exporter for FreeBSD.

[SuperQ]

Hrm, that file should probably have a build tag to avoid being used on FreeBSD.

[rfratto]

Ah, that makes sense since thermal zones are only used in Linux. It looks like sysfs is Linux specific, maybe all of the files in the sysfs package should have // +build linux instead of // +build !windows?