servo: Merge #20095 - Set CARGO_HOME for Windows builders (from servo:jdm-patch-9); r=jdm

This is a temporary fix to allow reopening the tree. This value belongs in saltfs instead, but it's already late and I don't want to have to wait to deploy the changes.

Source-Repo: https://github.com/servo/servo
Source-Revision: 036b9d313937cc1a053c0d94ccea1c2939ff09b0

--HG--
extra : subtree_source : https%3A//hg.mozilla.org/projects/converted-servo-linear
extra : subtree_revision : b03b6774f24897039b2dfd0d3948c899f134f583

servo/etc/ci/buildbot_steps.yml

@@ -189,6 +189,9 @@ arm64:
   - bash ./etc/ci/manifest_changed.sh
 
 windows-msvc-dev:
+  env:
+    CARGO_HOME: C:\buildbot\.cargo
+  commands:
   - mach.bat clean-cargo-cache --keep 3 --force
   - mach.bat clean-nightlies --keep 3 --force
   - mach.bat build --dev
@@ -198,6 +201,9 @@ windows-msvc-dev:
   - mach.bat test-stylo
 
 windows-msvc-nightly:
+  env:
+    CARGO_HOME: C:\buildbot\.cargo
+  commands:
   - mach.bat clean-cargo-cache --keep 3 --force
   - mach.bat clean-nightlies --keep 3 --force
   - mach.bat build --release