fix(ci): install the missing Rust dependency (#609)

Author: poemonsense

.github/workflows/nightly.yml

@@ -2,8 +2,8 @@ name: Nightly Regression
 
 on:
   schedule:
-    # run at 01:00 UTC (9:00 UTC+8) so that we can debug it immediately
-    - cron: '00 01 * * *'
+    # run at 00:00 UTC (8:00 UTC+8) so that we can debug it immediately
+    - cron: '00 00 * * *'
 
 jobs:
   test-difftest-fuzzing:
@@ -26,6 +26,8 @@ jobs:
         run: |
             cd $GITHUB_WORKSPACE/..
             git clone https://github.com/OpenXiangShan/xfuzz.git
+            curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y
+            source $HOME/.cargo/env
             cargo install cargo-make
             cd xfuzz && make init && make build