Use goreleaser to build and release (#244)

Instead of using gox on one side and an action to release, we can merge
them together with goreleaser which will build for extra targets (arm,
mips if needed in the future) and it also takes care of creating
checksums, a source archive, and a changelog and creating a release with
all the artifacts.

All binaries should respect the old naming convention, so any scripts
out there should still work.

Signed-off-by: Itxaka <igarcia@suse.com>

vendor/github.com/spf13/afero/copyOnWriteFs.go

@@ -14,7 +14,7 @@ var _ Lstater = (*CopyOnWriteFs)(nil)
 // a possibly writeable layer on top. Changes to the file system will only
 // be made in the overlay: Changing an existing file in the base layer which
 // is not present in the overlay will copy the file to the overlay ("changing"
-// includes also calls to e.g. Chtimes() and Chmod()).
+// includes also calls to e.g. Chtimes(), Chmod() and Chown()).
 //
 // Reading directories is currently only supported via Open(), not OpenFile().
 type CopyOnWriteFs struct {
@@ -75,6 +75,19 @@ func (u *CopyOnWriteFs) Chmod(name string, mode os.FileMode) error {
 	return u.layer.Chmod(name, mode)
 }
 
+func (u *CopyOnWriteFs) Chown(name string, uid, gid int) error {
+	b, err := u.isBaseFile(name)
+	if err != nil {
+		return err
+	}
+	if b {
+		if err := u.copyToLayer(name); err != nil {
+			return err
+		}
+	}
+	return u.layer.Chown(name, uid, gid)
+}
+
 func (u *CopyOnWriteFs) Stat(name string) (os.FileInfo, error) {
 	fi, err := u.layer.Stat(name)
 	if err != nil {
@@ -117,6 +130,26 @@ func (u *CopyOnWriteFs) LstatIfPossible(name string) (os.FileInfo, bool, error)
 	return fi, false, err
 }
 
+func (u *CopyOnWriteFs) SymlinkIfPossible(oldname, newname string) error {
+	if slayer, ok := u.layer.(Linker); ok {
+		return slayer.SymlinkIfPossible(oldname, newname)
+	}
+
+	return &os.LinkError{Op: "symlink", Old: oldname, New: newname, Err: ErrNoSymlink}
+}
+
+func (u *CopyOnWriteFs) ReadlinkIfPossible(name string) (string, error) {
+	if rlayer, ok := u.layer.(LinkReader); ok {
+		return rlayer.ReadlinkIfPossible(name)
+	}
+
+	if rbase, ok := u.base.(LinkReader); ok {
+		return rbase.ReadlinkIfPossible(name)
+	}
+
+	return "", &os.PathError{Op: "readlink", Path: name, Err: ErrNoReadlink}
+}
+
 func (u *CopyOnWriteFs) isNotExist(err error) bool {
 	if e, ok := err.(*os.PathError); ok {
 		err = e.Err