all: update build constraints to Go 1.17

Do it all at once in preparation for Go 1.18 support.

To make this commit, I've simply modified the `fmt-check` Makefile
target to rewrite files instead of listing the differences. So this is a
fully mechanical change, it should not have introduced any errors.

src/os/executable_procfs.go

@@ -4,6 +4,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build linux && !baremetal
 // +build linux,!baremetal
 
 package os