Fix configuration issue in CI runners (#23223)

While working on PR #23117, I noticed that the Windows runner in our CI
setup doesn't seem to respect the settings defined in
`.cargo/config.toml`. With @SomeoneToIgnore ’s help, Kirill and I
realized this issue isn’t limited to the Windows runner—all of our
runners disregard the configurations in `.cargo/config.toml`.

Later, @osiewicz suggested an excellent workaround. I conducted some
tests on PR #23117 and found that the solution works as intended.

Personally, I prefer using environment variables for global
configuration. However, according to the documentation
[here](https://doc.rust-lang.org/cargo/reference/config.html), it seems
that environment variables always override the settings in
`.cargo/config.toml`.

Release Notes:

- N/A

.github/workflows/ci.yml

@@ -20,7 +20,6 @@ env:
   CARGO_TERM_COLOR: always
   CARGO_INCREMENTAL: 0
   RUST_BACKTRACE: 1
-  RUSTFLAGS: "-D warnings"
 
 jobs:
   migration_checks:
@@ -101,6 +100,11 @@ jobs:
         with:
           clean: false
 
+      - name: Configure CI
+        run: |
+          mkdir -p ./../.cargo
+          cp ./.cargo/ci-config.toml ./../.cargo/config.toml
+
       - name: cargo clippy
         run: ./script/clippy
 
@@ -132,6 +136,11 @@ jobs:
           cargo build -p remote_server
           script/check-rust-livekit-macos
 
+      # Since the macOS runners are stateful, so we need to remove the config file to prevent potential bug.
+      - name: Clean CI config file
+        if: always()
+        run: rm -rf ./../.cargo
+
   linux_tests:
     timeout-minutes: 60
     name: (Linux) Run Clippy and tests
@@ -156,6 +165,11 @@ jobs:
       - name: Install Linux dependencies
         run: ./script/linux
 
+      - name: Configure CI
+        run: |
+          mkdir -p ./../.cargo
+          cp ./.cargo/ci-config.toml ./../.cargo/config.toml
+
       - name: cargo clippy
         run: ./script/clippy
 
@@ -167,6 +181,14 @@ jobs:
           cargo build -p zed
           cargo check -p workspace
 
+      # Even the Linux runner is not stateful, in theory there is no need to do this cleanup.
+      # But, to avoid potential issues in the future if we choose to use a stateful Linux runner and forget to add code
+      # to clean up the config file, I’ve included the cleanup code here as a precaution.
+      # While it’s not strictly necessary at this moment, I believe it’s better to err on the side of caution.
+      - name: Clean CI config file
+        if: always()
+        run: rm -rf ./../.cargo
+
   build_remote_server:
     timeout-minutes: 60
     name: (Linux) Build Remote Server
@@ -191,9 +213,18 @@ jobs:
       - name: Install Clang & Mold
         run: ./script/remote-server && ./script/install-mold 2.34.0
 
+      - name: Configure CI
+        run: |
+          mkdir -p ./../.cargo
+          cp ./.cargo/ci-config.toml ./../.cargo/config.toml
+
       - name: Build Remote Server
         run: cargo build -p remote_server
 
+      - name: Clean CI config file
+        if: always()
+        run: rm -rf ./../.cargo
+
   # todo(windows): Actually run the tests
   windows_tests:
     timeout-minutes: 60
@@ -215,6 +246,11 @@ jobs:
           save-if: ${{ github.ref == 'refs/heads/main' }}
           cache-provider: "github"
 
+      - name: Configure CI
+        run: |
+          mkdir -p ./../.cargo
+          cp ./.cargo/ci-config.toml ./../.cargo/config.toml
+
       - name: cargo clippy
         # Windows can't run shell scripts, so we need to use `cargo xtask`.
         run: cargo xtask clippy
@@ -222,6 +258,11 @@ jobs:
       - name: Build Zed
         run: cargo build
 
+      # Since the Windows runners are stateful, so we need to remove the config file to prevent potential bug.
+      - name: Clean CI config file
+        if: always()
+        run: Remove-Item -Path "./../.cargo" -Recurse -Force
+
   bundle-mac:
     timeout-minutes: 120
     name: Create a macOS bundle