Remove dependencies on xwin and zig.  We're not offering cross-compilation
options using these crates.

diff --git a/Cargo.toml b/Cargo.toml
index 6cbdca3..22ea5ef 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -76,16 +76,6 @@ version = "0.1.4"
 [dependencies.cargo-options]
 version = "0.6.0"
 
-[dependencies.cargo-xwin]
-version = "0.14.3"
-optional = true
-default-features = false
-
-[dependencies.cargo-zigbuild]
-version = "0.16.10"
-optional = true
-default-features = false
-
 [dependencies.cargo_metadata]
 version = "0.15.3"
 
@@ -310,8 +300,6 @@ version = "4.3.0"
 [features]
 cli-completion = ["dep:clap_complete_command"]
 cross-compile = [
-    "zig",
-    "xwin",
 ]
 default = [
     "full",
@@ -330,7 +318,6 @@ log = ["tracing-subscriber"]
 native-tls = [
     "dep:native-tls",
     "ureq?/native-tls",
-    "cargo-xwin?/native-tls",
     "dep:rustls-pemfile",
 ]
 password-storage = [
@@ -340,7 +327,6 @@ password-storage = [
 rustls = [
     "dep:rustls",
     "ureq?/tls",
-    "cargo-xwin?/rustls-tls",
     "dep:rustls-pemfile",
 ]
 scaffolding = [
@@ -358,5 +344,3 @@ upload = [
     "wild",
     "dep:dirs",
 ]
-xwin = ["cargo-xwin"]
-zig = ["cargo-zigbuild"]
s/offload.scm'>log</a><a href='/guix/tree/tests/offload.scm?id=6e174c4edd4786d93c1e424c45052f70b2bb3fb0'>tree</a><a href='/guix/commit/tests/offload.scm?id=6e174c4edd4786d93c1e424c45052f70b2bb3fb0'>commit</a><a href='/guix/diff/tests/offload.scm?id=6e174c4edd4786d93c1e424c45052f70b2bb3fb0'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/tests/offload.scm'>
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<div class='path'>path: <a href='/guix/log/?id=6e174c4edd4786d93c1e424c45052f70b2bb3fb0'>root</a>/<a href='/guix/log/tests?id=6e174c4edd4786d93c1e424c45052f70b2bb3fb0'>tests</a>/<a href='/guix/log/tests/offload.scm?id=6e174c4edd4786d93c1e424c45052f70b2bb3fb0'>offload.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/tests/offload.scm?id=6e174c4edd4786d93c1e424c45052f70b2bb3fb0&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2020-08-25 13:45:27 -0400'>2020-08-25</span></td><td><a href='/guix/commit/tests/offload.scm?id=4b5a6fbc9b754c0ca70d033dd99f17c4f028733a'>offload: Modify the build-machine record to accept multiple systems.</a><span class='msg-avail'>...<span class='msg-tooltip'>* guix/scripts/offload.scm (&lt;build-machine&gt;)[systems]: New field.
[system]: Accessor changed to %build-machine-system.  Default to #f.
* guix/scripts/offload.scm (build-machine-system): Wrap %build-machine-system
with a deprecation warning.
(build-machine-systems): Access the new systems field or fallback to use
build-machine-system, for backward compatibility.
(machine-matches?): Adjust.
* tests/offload.scm: Add tests...
* Makefile.am (SCM_TESTS): ...and register them.
* doc/guix.texi (Daemon Offload Setup): Update doc.
</span></span></td><td>Maxim Cournoyer</td></tr>
ce): Likewise.
* guix/cve.scm (json-&gt;cve-items): Likewise.
* guix/git-authenticate.scm (commit-signing-key): Likewise.
(commit-authorized-keys): Likewise.
(authenticate-commit): Likewise.
(verify-introductory-commit): Likewise.
* guix/remote.scm (remote-pipe-for-gexp): Likewise.
* guix/scripts/graph.scm (assert-package): Likewise.
* guix/scripts/offload.scm (private-key-from-file*): Likewise.
* guix/ssh.scm (authenticate-server*): Likewise.
(open-ssh-session): Likewise.
(remote-inferior): Likewise.
* guix/ui.scm (matching-generations): Likewise.
* guix/upstream.scm (package-update): Likewise.
* tests/channels.scm ("latest-channel-instances, missing introduction for 'guix'"):
Catch 'formatted-message?'.
("authenticate-channel, wrong first commit signer"): Likewise.
* tests/lint.scm ("patches: not found"): Adjust message string.
* tests/packages.scm ("patch not found yields a run-time error"): Catch
'formatted-message?'.
* guix/lint.scm (check-patch-file-names): Handle 'formatted-message?'.
(check-derivation): Ditto.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-07-25 19:11:36 +0200'>2020-07-25</span></td><td><a href='/guix/commit/gnu.scm?id=f9a8dd053c4e0fd1fc4b64291bb90de36520b3bc'>utils: Move '&amp;fix-hint' to (guix diagnostics).</a><span class='msg-avail'>...<span class='msg-tooltip'>* guix/utils.scm (&amp;fix-hint): Move to...
* guix/diagnostics.scm (&amp;fix-hint): ... here.
* gnu.scm: Adjust imports accordingly.
* gnu/system/mapped-devices.scm: Likewise.
* guix/channels.scm: Likewise.
* guix/profiles.scm: Likewise.
* guix/scripts/system/reconfigure.scm: Likewise.
* guix/ssh.scm: Likewise.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-07-25 19:11:36 +0200'>2020-07-25</span></td><td><a href='/guix/commit/gnu.scm?id=a5e2fc73760a2ae023f2e56bdbf8025971f90e64'>utils: Move &lt;location&gt; and '&amp;error-location' to (guix diagnostics).</a><span class='msg-avail'>...<span class='msg-tooltip'>* guix/utils.scm (&lt;location&gt;, source-properties-&gt;location)
(location-&gt;source-properties, &amp;error-location): Move to...
* guix/diagnostics.scm: ... here.
* gnu.scm: Adjust imports accordingly.
* gnu/machine.scm: Likewise.
* gnu/system.scm: Likewise.
* gnu/tests.scm: Likewise.
* guix/inferior.scm: Likewise.
* tests/channels.scm: Likewise.
* tests/packages.scm: Likewise.
</span></span></td><td>Ludovic Courtès</td></tr>