xattr: Disallow build on non linux platforms

Signed-off-by: Harshavardhana <fharshav@redhat.com>

xattr/xattr_unsupported.go

@@ -0,0 +1,15 @@
+// +build !linux
+
+package xattr
+
+func Listxattr(path string) ([]string, error) {
+	return nil, ErrNotSupportedPlatform
+}
+
+func Getxattr(path, attr string) (string, error) {
+	return "", ErrNotSupportedPlatform
+}
+
+func Setxattr(path, xattr, value string) error {
+	return ErrNotSupportedPlatform
+}