remove "apparmor" build tag (Always compile AppArmor support)

The apparmor tag was introduced in a01ed80 (2014) to make cgo dependency
on libapparmor optional.

However, the cgo dependency was removed in db093f6 (2017), so it is no
longer meaningful to keep apparmor build tag.

Close #2704

Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>

Makefile

@@ -9,7 +9,7 @@ GIT_BRANCH := $(shell git rev-parse --abbrev-ref HEAD 2>/dev/null)
 GIT_BRANCH_CLEAN := $(shell echo $(GIT_BRANCH) | sed -e "s/[^[:alnum:]]/-/g")
 RUNC_IMAGE := runc_dev$(if $(GIT_BRANCH_CLEAN),:$(GIT_BRANCH_CLEAN))
 PROJECT := github.com/opencontainers/runc
-BUILDTAGS ?= seccomp selinux apparmor
+BUILDTAGS ?= seccomp selinux
 COMMIT_NO := $(shell git rev-parse HEAD 2> /dev/null || true)
 COMMIT ?= $(if $(shell git status --porcelain --untracked-files=no),"$(COMMIT_NO)-dirty","$(COMMIT_NO)")
 VERSION := $(shell cat ./VERSION)

README.md

@@ -63,16 +63,17 @@ To change build tags from the default, set the `BUILDTAGS` variable for make,
 e.g.
 
 ```bash
-make BUILDTAGS='seccomp apparmor'
+make BUILDTAGS='seccomp'
 ```
 
 | Build Tag | Feature                            | Enabled by default | Dependency |
 |-----------|------------------------------------|--------------------|------------|
 | seccomp   | Syscall filtering                  | yes                | libseccomp |
 | selinux   | selinux process and mount labeling | yes                | <none>     |
-| apparmor  | apparmor profile support           | yes                | <none>     |
 | nokmem    | disable kernel memory accounting   | no                 | <none>     |
 
+The following build tags were used earlier, but are now obsoleted:
+ - **apparmor** (since runc v1.0.0-rc93 the feature is always enabled)
 
 ### Running the test suite
 

libcontainer/apparmor/apparmor_linux.go

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

libcontainer/apparmor/apparmor_unsupported.go

@@ -1,4 +1,4 @@
-// +build !apparmor !linux
+// +build !linux
 
 package apparmor
 

script/release.sh

@@ -27,7 +27,7 @@ function build_project() {
 	builddir="$(dirname "$1")"
 
 	# Build with all tags enabled.
-	make -C "$root" COMMIT_NO= BUILDTAGS="seccomp selinux apparmor" static
+	make -C "$root" COMMIT_NO= BUILDTAGS="seccomp selinux" static
 	mv "$root/$project" "$1"
 }