support compilation for armv7

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

vendor.conf

@@ -13,7 +13,7 @@ github.com/golang/protobuf 8ee79997227bf9b34611aee7946ae64735e6fd93
 github.com/opencontainers/runc ce450bcc6c135cae93ee2a99d41a308c179ff6dc
 github.com/opencontainers/runtime-spec v1.0.0-rc3
 github.com/Sirupsen/logrus v0.11.0
-github.com/stevvooe/go-btrfs 8539a1d04898663b8eda14982e24b74e7a12388e
+github.com/stevvooe/go-btrfs ea304655a3ed8f00773db1844f921d12541ee0d1
 github.com/stretchr/testify v1.1.4
 github.com/davecgh/go-spew v1.1.0
 github.com/pmezard/go-difflib v1.0.0
@@ -26,7 +26,7 @@ github.com/nightlyone/lockfile 1d49c987357a327b5b03aa84cbddd582c328615d
 github.com/opencontainers/go-digest 21dfd564fd89c944783d00d069f33e3e7123c448
 golang.org/x/sys/unix d75a52659825e75fff6158388dddc6a5b04f9ba5
 github.com/opencontainers/image-spec a431dbcf6a74fca2e0e040b819a836dbe3fb23ca
-github.com/stevvooe/continuity 1530f13d23b34e2ccaf33881fefecc7e28e3577b
+github.com/stevvooe/continuity 577e137350afb00343495f55bb8671fe7e22b0bf
 golang.org/x/sync 450f422ab23cf9881c94e2db30cac0eb1b7cf80c
 github.com/BurntSushi/toml      v0.2.0-21-g9906417
 github.com/grpc-ecosystem/go-grpc-prometheus 6b7015e65d366bf3f19b2b2a000a831940f0f7e0