update to latest rules_rust incremental compilation

.bazelrc

@@ -28,15 +28,11 @@ build --incompatible_default_to_explicit_init_py
 
 build:ci --show_timestamps --isatty=0 --color=yes --show_progress_rate_limit=5
 
-# incrementally compile Anki crates in fastbuild mode, but not release mode.
+# disable incremental compilation in release mode
-# The worker must be separately enabled; see docs/development.md
+build:opt -c opt --@rules_rust//:experimental_incremental_prefixes=
-build -c fastbuild --@rules_rust//worker:include_regex=anki.*|rsbridge
-build:opt -c opt --@rules_rust//worker:include_regex=no-crates-please
-build --worker_max_instances=Rustc=HOST_CPUS*0.5
 
 # the TypeScript workers on Windows choke when deps are changed while they're
-# still running, so shut them down at the end of the build. Also fixes issues
+# still running, so shut them down at the end of the build.
-# with the optional Rust worker.
 build:windows --worker_quit_after_build
 
 try-import %workspace%/user.bazelrc

docs/development.md

@@ -153,7 +153,7 @@ following in your user.bazelrc file to enable incremental compilation
 when using ./run.
 
 ```
-build --@rules_rust//worker:cache_root=/path/to/folder/to/store/temp/files
+build --@rules_rust//:experimental_incremental_base=/home/myuser/bazel/incremental
 ```
 
 The worker support is experimental, so you may need to remove it in future

repos.bzl

@@ -33,11 +33,11 @@ def register_repos():
     maybe(
         http_archive,
         name = "rules_rust",
-        strip_prefix = "rules_rust-anki-2021-03-30",
+        strip_prefix = "rules_rust-anki-2021-04-09",
         urls = [
-            "https://github.com/ankitects/rules_rust/archive/anki-2021-03-30.tar.gz",
+            "https://github.com/ankitects/rules_rust/archive/anki-2021-04-09.tar.gz",
         ],
-        sha256 = "ad6286615fd21f71db4490207aa8d5ecdf5f526643cd65d682458d92aa84ff85",
+        sha256 = "2821b22e065c1b4dc73610b1d6ccbed7ed4d755b316e7e0641cd079b7abe4900",
     )
 
     # python