Changes

Summary

1. hack/env: mount a volume for /tmp (commit: e29078d) (details)
2. hack/lib: dedup os::util::host_platform and os::build::host_platform (commit: 2b44ff7) (details)

Commit e29078d11aaa1c25773acd37637a63cf5fad0d22 by jdetiber hack/env: mount a volume for /tmp (commit: e29078d)
	images/release/golang-1.9/Dockerfile (diff)
	hack/lib/build/environment.sh (diff)
	images/release/golang-1.8/Dockerfile (diff)
	images/release/golang-1.7/Dockerfile (diff)
Commit 2b44ff73c43a2a0924085f36ee9150fbf6ee8404 by jdetiber hack/lib: dedup os::util::host_platform and os::build::host_platform (commit: 2b44ff7)
	hack/lib/util/misc.sh (diff)
	hack/lib/cleanup.sh (diff)
	hack/lib/util/environment.sh (diff)
	CONTRIBUTING.adoc (diff)