Update "library()" to reference new multiarch branches (#354)
Update "library()" to reference new multiarch branches (#354)

Example output:

```console
$ ./build library

# autogenerated by https://github.com/gliderlabs/docker-alpine/blob/master/build

Maintainers: Glider Labs <d25187dc137f35c88bc80ec8c3ffbdb17b5eb873@gliderlabs.com> (@gliderlabs)
GitRepo: https://github.com/gliderlabs/docker-alpine.git
GitFetch: refs/heads/release
GitCommit: f2e9aa97b32b3f537dca61da066711d3b017ab3a

Tags: 3.6, latest
Architectures: arm64v8, arm32v6, ppc64le, s390x, amd64, i386
arm64v8-GitFetch: refs/heads/rootfs/library-3.6/aarch64
arm64v8-GitCommit: 23170e382bf9f6e6a10a5618101f1a434586ba52
arm64v8-Directory: versions/library-3.6/aarch64
arm32v6-GitFetch: refs/heads/rootfs/library-3.6/armhf
arm32v6-GitCommit: 57548db3751630dc3548454a873f500cecb156eb
arm32v6-Directory: versions/library-3.6/armhf
ppc64le-GitFetch: refs/heads/rootfs/library-3.6/ppc64le
ppc64le-GitCommit: 34b61e92daf792d06592aa88fb78e353af757434
ppc64le-Directory: versions/library-3.6/ppc64le
s390x-GitFetch: refs/heads/rootfs/library-3.6/s390x
s390x-GitCommit: f2596f5e54c2eee1b37dc42b83422a9a4a09e16d
s390x-Directory: versions/library-3.6/s390x
amd64-GitFetch: refs/heads/rootfs/library-3.6/x86_64
amd64-GitCommit: 0450fe826ccdedf63dd70da1ad953f1aaf932225
amd64-Directory: versions/library-3.6/x86_64
i386-GitFetch: refs/heads/rootfs/library-3.6/x86
i386-GitCommit: ec586c792873b3f09fd0c50f6ace0b61aad60eb2
i386-Directory: versions/library-3.6/x86

Tags: edge
Architectures: arm64v8, arm32v6, ppc64le, s390x, amd64, i386
arm64v8-GitFetch: refs/heads/rootfs/library-edge/aarch64
arm64v8-GitCommit: 1903a85da34bcd78249ce2b2204f0f7fe22c9489
arm64v8-Directory: versions/library-edge/aarch64
arm32v6-GitFetch: refs/heads/rootfs/library-edge/armhf
arm32v6-GitCommit: afa0aaacb6cc77e0be9696dc8c026fe1fcbfa44d
arm32v6-Directory: versions/library-edge/armhf
ppc64le-GitFetch: refs/heads/rootfs/library-edge/ppc64le
ppc64le-GitCommit: 474a968a0ccbba9e3b20ffb0338337af8b9348b2
ppc64le-Directory: versions/library-edge/ppc64le
s390x-GitFetch: refs/heads/rootfs/library-edge/s390x
s390x-GitCommit: b9345dae00ffa7a7061f9b7c4cb64a7ee7a90a3c
s390x-Directory: versions/library-edge/s390x
amd64-GitFetch: refs/heads/rootfs/library-edge/x86_64
amd64-GitCommit: 1aa169fe8d573c0b6d8fe0d446f61be0700c8008
amd64-Directory: versions/library-edge/x86_64
i386-GitFetch: refs/heads/rootfs/library-edge/x86
i386-GitCommit: d17079a97138109d5ef48206f8fa276090d3e49d
i386-Directory: versions/library-edge/x86

Tags: 3.1
Architectures: amd64
amd64-GitFetch: refs/heads/rootfs/library-3.1
amd64-GitCommit: 956c360824ed3629d8e132e1c13299be73120f88
amd64-Directory: versions/library-3.1

Tags: 3.2
Architectures: amd64
amd64-GitFetch: refs/heads/rootfs/library-3.2
amd64-GitCommit: 8708779d075ac943b5d57b60cf17a6d2dacfbf1b
amd64-Directory: versions/library-3.2

Tags: 3.3
Architectures: amd64
amd64-GitFetch: refs/heads/rootfs/library-3.3
amd64-GitCommit: b8e69ac308464f18e5fc8fb2da827f7e97c890ff
amd64-Directory: versions/library-3.3

Tags: 3.4
Architectures: amd64
amd64-GitFetch: refs/heads/rootfs/library-3.4
amd64-GitCommit: c32ca6c6c399fe7d2ba857635ea15d0b08ac6dc5
amd64-Directory: versions/library-3.4

Tags: 3.5
Architectures: amd64
amd64-GitFetch: refs/heads/rootfs/library-3.5
amd64-GitCommit: 849c93d4bd1c5490dfd146f24291a40aa430d0ed
amd64-Directory: versions/library-3.5

```
gliderlabs/docker-alpine