Rm build tags from main pkg

This was added by commit 5aa82c950 back in the day when we thought
runc is going to be cross-platform. It's very clear now it's Linux-only
package.

While at it, further clarify it in README that we're Linux only.

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

README.md

@@ -8,7 +8,7 @@
 
 ## Introduction
 
-`runc` is a CLI tool for spawning and running containers according to the OCI specification.
+`runc` is a CLI tool for spawning and running containers on Linux according to the OCI specification.
 
 ## Releases
 
@@ -23,8 +23,7 @@ A third party security audit was performed by Cure53, you can see the full repor
 
 ## Building
 
-`runc` currently supports the Linux platform with various architecture support.
+`runc` only supports Linux. It must be built with Go version 1.15 or higher.
-It must be built with Go version 1.15 or higher.
 
 In order to enable seccomp support you will need to install `libseccomp` on your platform.
 > e.g. `libseccomp-devel` for CentOS, or `libseccomp-dev` for Ubuntu

checkpoint.go

@@ -1,5 +1,3 @@
-// +build linux
-
 package main
 
 import (

delete.go

@@ -1,5 +1,3 @@
-// +build !solaris
-
 package main
 
 import (

events.go

@@ -1,5 +1,3 @@
-// +build linux
-
 package main
 
 import (

exec.go

@@ -1,5 +1,3 @@
-// +build linux
-
 package main
 
 import (

kill.go

@@ -1,5 +1,3 @@
-// +build linux
-
 package main
 
 import (

list.go

@@ -1,5 +1,3 @@
-// +build linux
-
 package main
 
 import (

notify_socket.go

@@ -1,5 +1,3 @@
-// +build linux
-
 package main
 
 import (

pause.go

@@ -1,5 +1,3 @@
-// +build linux
-
 package main
 
 import (

ps.go

@@ -1,5 +1,3 @@
-// +build linux
-
 package main
 
 import (

restore.go

@@ -1,5 +1,3 @@
-// +build linux
-
 package main
 
 import (

run.go

@@ -1,5 +1,3 @@
-// +build linux
-
 package main
 
 import (

signals.go

@@ -1,5 +1,3 @@
-// +build linux
-
 package main
 
 import (

spec.go

@@ -1,5 +1,3 @@
-// +build linux
-
 package main
 
 import (

state.go

@@ -1,5 +1,3 @@
-// +build linux
-
 package main
 
 import (

tty.go

@@ -1,5 +1,3 @@
-// +build linux
-
 package main
 
 import (

update.go

@@ -1,5 +1,3 @@
-// +build linux
-
 package main
 
 import (