Bug 1546870 - Package win*-rust toolchains as .tar.xz. r=froydnj

This uniformizes the artifact name across platforms. We may want to do
the same for other toolchains, but it bears the question whether xz is
reliably available on users' Windows machines, while it doesn't matter
for rust, since mach bootstrap pulls it with rustup rather than from
automation, contrary to other toolchains.

Differential Revision: https://phabricator.services.mozilla.com/D28780

--HG--
extra : moz-landing-system : lando

taskcluster/ci/toolchain/rust.yml

@@ -148,7 +148,6 @@ win64-rust-1.28:
             '--target', 'x86_64-pc-windows-msvc',
             '--target', 'i686-pc-windows-msvc',
         ]
-        toolchain-artifact: public/build/rustc.tar.bz2
 
 win64-rust-1.34:
     treeherder:
@@ -162,7 +161,6 @@ win64-rust-1.34:
             '--target', 'aarch64-pc-windows-msvc',
         ]
         toolchain-alias: win64-rust
-        toolchain-artifact: public/build/rustc.tar.bz2
 
 win64-rust-nightly:
     description: "rust nightly repack"
@@ -175,7 +173,6 @@ win64-rust-nightly:
             '--target', 'x86_64-pc-windows-msvc',
             '--target', 'i686-pc-windows-msvc',
         ]
-        toolchain-artifact: public/build/rustc.tar.bz2
 
 mingw32-rust-1.31:
     treeherder:

taskcluster/scripts/misc/repack_rust.py

@@ -240,12 +240,8 @@ def fetch_optional(manifest, pkg, host):
 
 
 def tar_for_host(host):
-    if 'linux' in host:
-        tar_options = 'cJf'
-        tar_ext = '.tar.xz'
-    else:
-        tar_options = 'cjf'
-        tar_ext = '.tar.bz2'
+    tar_options = 'cJf'
+    tar_ext = '.tar.xz'
     return tar_options, tar_ext