Read an xz release in Go, so the build seat needs no xz tool (hq issue 345)

Betterbird's pinned .tar.xz failed on the build seat with "this build seat has
no xz to read it": the seat's image is the catalogue's build-agent recipe,
which installs git and docker-cli alone, and xz had been added only to
cmd/mesh-builder/Dockerfile, which the seat does not build from. The stream
is now read with github.com/ulikunitz/xz (vendored), its dictionary capped
at xz's own largest preset, and what it unpacks to bounded as before; the
xz line in the unused Dockerfile is taken back out.

vendor/github.com/ulikunitz/xz/internal/hash/cyclic_poly.go

@@ -0,0 +1,181 @@
+// Copyright 2014-2022 Ulrich Kunitz. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package hash
+
+// CyclicPoly provides a cyclic polynomial rolling hash.
+type CyclicPoly struct {
+	h uint64
+	p []uint64
+	i int
+}
+
+// ror rotates the unsigned 64-bit integer to right. The argument s must be
+// less than 64.
+func ror(x uint64, s uint) uint64 {
+	return (x >> s) | (x << (64 - s))
+}
+
+// NewCyclicPoly creates a new instance of the CyclicPoly structure. The
+// argument n gives the number of bytes for which a hash will be executed.
+// This number must be positive; the method panics if this isn't the case.
+func NewCyclicPoly(n int) *CyclicPoly {
+	if n < 1 {
+		panic("argument n must be positive")
+	}
+	return &CyclicPoly{p: make([]uint64, 0, n)}
+}
+
+// Len returns the length of the byte sequence for which a hash is generated.
+func (r *CyclicPoly) Len() int {
+	return cap(r.p)
+}
+
+// RollByte hashes the next byte and returns a hash value. The complete becomes
+// available after at least Len() bytes have been hashed.
+func (r *CyclicPoly) RollByte(x byte) uint64 {
+	y := hash[x]
+	if len(r.p) < cap(r.p) {
+		r.h = ror(r.h, 1) ^ y
+		r.p = append(r.p, y)
+	} else {
+		r.h ^= ror(r.p[r.i], uint(cap(r.p)-1))
+		r.h = ror(r.h, 1) ^ y
+		r.p[r.i] = y
+		r.i = (r.i + 1) % cap(r.p)
+	}
+	return r.h
+}
+
+// Stores the hash for the individual bytes.
+var hash = [256]uint64{
+	0x2e4fc3f904065142, 0xc790984cfbc99527,
+	0x879f95eb8c62f187, 0x3b61be86b5021ef2,
+	0x65a896a04196f0a5, 0xc5b307b80470b59e,
+	0xd3bff376a70df14b, 0xc332f04f0b3f1701,
+	0x753b5f0e9abf3e0d, 0xb41538fdfe66ef53,
+	0x1906a10c2c1c0208, 0xfb0c712a03421c0d,
+	0x38be311a65c9552b, 0xfee7ee4ca6445c7e,
+	0x71aadeded184f21e, 0xd73426fccda23b2d,
+	0x29773fb5fb9600b5, 0xce410261cd32981a,
+	0xfe2848b3c62dbc2d, 0x459eaaff6e43e11c,
+	0xc13e35fc9c73a887, 0xf30ed5c201e76dbc,
+	0xa5f10b3910482cea, 0x2945d59be02dfaad,
+	0x06ee334ff70571b5, 0xbabf9d8070f44380,
+	0xee3e2e9912ffd27c, 0x2a7118d1ea6b8ea7,
+	0x26183cb9f7b1664c, 0xea71dac7da068f21,
+	0xea92eca5bd1d0bb7, 0x415595862defcd75,
+	0x248a386023c60648, 0x9cf021ab284b3c8a,
+	0xfc9372df02870f6c, 0x2b92d693eeb3b3fc,
+	0x73e799d139dc6975, 0x7b15ae312486363c,
+	0xb70e5454a2239c80, 0x208e3fb31d3b2263,
+	0x01f563cabb930f44, 0x2ac4533d2a3240d8,
+	0x84231ed1064f6f7c, 0xa9f020977c2a6d19,
+	0x213c227271c20122, 0x09fe8a9a0a03d07a,
+	0x4236dc75bcaf910c, 0x460a8b2bead8f17e,
+	0xd9b27be1aa07055f, 0xd202d5dc4b11c33e,
+	0x70adb010543bea12, 0xcdae938f7ea6f579,
+	0x3f3d870208672f4d, 0x8e6ccbce9d349536,
+	0xe4c0871a389095ae, 0xf5f2a49152bca080,
+	0x9a43f9b97269934e, 0xc17b3753cb6f475c,
+	0xd56d941e8e206bd4, 0xac0a4f3e525eda00,
+	0xa06d5a011912a550, 0x5537ed19537ad1df,
+	0xa32fe713d611449d, 0x2a1d05b47c3b579f,
+	0x991d02dbd30a2a52, 0x39e91e7e28f93eb0,
+	0x40d06adb3e92c9ac, 0x9b9d3afde1c77c97,
+	0x9a3f3f41c02c616f, 0x22ecd4ba00f60c44,
+	0x0b63d5d801708420, 0x8f227ca8f37ffaec,
+	0x0256278670887c24, 0x107e14877dbf540b,
+	0x32c19f2786ac1c05, 0x1df5b12bb4bc9c61,
+	0xc0cac129d0d4c4e2, 0x9fdb52ee9800b001,
+	0x31f601d5d31c48c4, 0x72ff3c0928bcaec7,
+	0xd99264421147eb03, 0x535a2d6d38aefcfe,
+	0x6ba8b4454a916237, 0xfa39366eaae4719c,
+	0x10f00fd7bbb24b6f, 0x5bd23185c76c84d4,
+	0xb22c3d7e1b00d33f, 0x3efc20aa6bc830a8,
+	0xd61c2503fe639144, 0x30ce625441eb92d3,
+	0xe5d34cf359e93100, 0xa8e5aa13f2b9f7a5,
+	0x5c2b8d851ca254a6, 0x68fb6c5e8b0d5fdf,
+	0xc7ea4872c96b83ae, 0x6dd5d376f4392382,
+	0x1be88681aaa9792f, 0xfef465ee1b6c10d9,
+	0x1f98b65ed43fcb2e, 0x4d1ca11eb6e9a9c9,
+	0x7808e902b3857d0b, 0x171c9c4ea4607972,
+	0x58d66274850146df, 0x42b311c10d3981d1,
+	0x647fa8c621c41a4c, 0xf472771c66ddfedc,
+	0x338d27e3f847b46b, 0x6402ce3da97545ce,
+	0x5162db616fc38638, 0x9c83be97bc22a50e,
+	0x2d3d7478a78d5e72, 0xe621a9b938fd5397,
+	0x9454614eb0f81c45, 0x395fb6e742ed39b6,
+	0x77dd9179d06037bf, 0xc478d0fee4d2656d,
+	0x35d9d6cb772007af, 0x83a56e92c883f0f6,
+	0x27937453250c00a1, 0x27bd6ebc3a46a97d,
+	0x9f543bf784342d51, 0xd158f38c48b0ed52,
+	0x8dd8537c045f66b4, 0x846a57230226f6d5,
+	0x6b13939e0c4e7cdf, 0xfca25425d8176758,
+	0x92e5fc6cd52788e6, 0x9992e13d7a739170,
+	0x518246f7a199e8ea, 0xf104c2a71b9979c7,
+	0x86b3ffaabea4768f, 0x6388061cf3e351ad,
+	0x09d9b5295de5bbb5, 0x38bf1638c2599e92,
+	0x1d759846499e148d, 0x4c0ff015e5f96ef4,
+	0xa41a94cfa270f565, 0x42d76f9cb2326c0b,
+	0x0cf385dd3c9c23ba, 0x0508a6c7508d6e7a,
+	0x337523aabbe6cf8d, 0x646bb14001d42b12,
+	0xc178729d138adc74, 0xf900ef4491f24086,
+	0xee1a90d334bb5ac4, 0x9755c92247301a50,
+	0xb999bf7c4ff1b610, 0x6aeeb2f3b21e8fc9,
+	0x0fa8084cf91ac6ff, 0x10d226cf136e6189,
+	0xd302057a07d4fb21, 0x5f03800e20a0fcc3,
+	0x80118d4ae46bd210, 0x58ab61a522843733,
+	0x51edd575c5432a4b, 0x94ee6ff67f9197f7,
+	0x765669e0e5e8157b, 0xa5347830737132f0,
+	0x3ba485a69f01510c, 0x0b247d7b957a01c3,
+	0x1b3d63449fd807dc, 0x0fdc4721c30ad743,
+	0x8b535ed3829b2b14, 0xee41d0cad65d232c,
+	0xe6a99ed97a6a982f, 0x65ac6194c202003d,
+	0x692accf3a70573eb, 0xcc3c02c3e200d5af,
+	0x0d419e8b325914a3, 0x320f160f42c25e40,
+	0x00710d647a51fe7a, 0x3c947692330aed60,
+	0x9288aa280d355a7a, 0xa1806a9b791d1696,
+	0x5d60e38496763da1, 0x6c69e22e613fd0f4,
+	0x977fc2a5aadffb17, 0xfb7bd063fc5a94ba,
+	0x460c17992cbaece1, 0xf7822c5444d3297f,
+	0x344a9790c69b74aa, 0xb80a42e6cae09dce,
+	0x1b1361eaf2b1e757, 0xd84c1e758e236f01,
+	0x88e0b7be347627cc, 0x45246009b7a99490,
+	0x8011c6dd3fe50472, 0xc341d682bffb99d7,
+	0x2511be93808e2d15, 0xd5bc13d7fd739840,
+	0x2a3cd030679ae1ec, 0x8ad9898a4b9ee157,
+	0x3245fef0a8eaf521, 0x3d6d8dbbb427d2b0,
+	0x1ed146d8968b3981, 0x0c6a28bf7d45f3fc,
+	0x4a1fd3dbcee3c561, 0x4210ff6a476bf67e,
+	0xa559cce0d9199aac, 0xde39d47ef3723380,
+	0xe5b69d848ce42e35, 0xefa24296f8e79f52,
+	0x70190b59db9a5afc, 0x26f166cdb211e7bf,
+	0x4deaf2df3c6b8ef5, 0xf171dbdd670f1017,
+	0xb9059b05e9420d90, 0x2f0da855c9388754,
+	0x611d5e9ab77949cc, 0x2912038ac01163f4,
+	0x0231df50402b2fba, 0x45660fc4f3245f58,
+	0xb91cc97c7c8dac50, 0xb72d2aafe4953427,
+	0xfa6463f87e813d6b, 0x4515f7ee95d5c6a2,
+	0x1310e1c1a48d21c3, 0xad48a7810cdd8544,
+	0x4d5bdfefd5c9e631, 0xa43ed43f1fdcb7de,
+	0xe70cfc8fe1ee9626, 0xef4711b0d8dda442,
+	0xb80dd9bd4dab6c93, 0xa23be08d31ba4d93,
+	0x9b37db9d0335a39c, 0x494b6f870f5cfebc,
+	0x6d1b3c1149dda943, 0x372c943a518c1093,
+	0xad27af45e77c09c4, 0x3b6f92b646044604,
+	0xac2917909f5fcf4f, 0x2069a60e977e5557,
+	0x353a469e71014de5, 0x24be356281f55c15,
+	0x2b6d710ba8e9adea, 0x404ad1751c749c29,
+	0xed7311bf23d7f185, 0xba4f6976b4acc43e,
+	0x32d7198d2bc39000, 0xee667019014d6e01,
+	0x494ef3e128d14c83, 0x1f95a152baecd6be,
+	0x201648dff1f483a5, 0x68c28550c8384af6,
+	0x5fc834a6824a7f48, 0x7cd06cb7365eaf28,
+	0xd82bbd95e9b30909, 0x234f0d1694c53f6d,
+	0xd2fb7f4a96d83f4a, 0xff0d5da83acac05e,
+	0xf8f6b97f5585080a, 0x74236084be57b95b,
+	0xa25e40c03bbc36ad, 0x6b6e5c14ce88465b,
+	0x4378ffe93e1528c5, 0x94ca92a17118e2d2,
+}