fix CI "build wheels" step for rustup no longer installing default toolchain (Cherry-pick of #22037) (#22039)

Fix the "Build wheels" step for a breaking change in [Rustup
v1.28.0](https://blog.rust-lang.org/2025/03/02/Rustup-1.28.0.html) which
no longer installs a default toolchain any more.

Use `rustup default` to install the applicable toolchain because it is
idempotent and will install the toolchain if it is not already
installed. `rustup toolchain install` by design will try to install even
if the toolchain is already installed. See
rust-lang/rustup#710 for discussion of this
distinction.

Closes #22036

---------

Co-authored-by: Tom Dyas <[email protected]>

Author: WorkerPants

.github/workflows/release.yaml

@@ -35,6 +35,15 @@ jobs:
 
         echo "${HOME}/.cargo/bin" >> $GITHUB_PATH
 
+        '
+    - name: Install Rust toolchain
+      run: '# Set the default toolchain. Installs the toolchain if it is not already
+        installed.
+
+        rustup default 1.82.0
+
+        cargo version
+
         '
     - name: Expose Pythons
       run: 'echo "/opt/python/cp37-cp37m/bin" >> $GITHUB_PATH
@@ -116,6 +125,15 @@ jobs:
 
         echo "${HOME}/.cargo/bin" >> $GITHUB_PATH
 
+        '
+    - name: Install Rust toolchain
+      run: '# Set the default toolchain. Installs the toolchain if it is not already
+        installed.
+
+        rustup default 1.82.0
+
+        cargo version
+
         '
     - name: Expose Pythons
       run: 'echo "/opt/python/cp37-cp37m/bin" >> $GITHUB_PATH

.github/workflows/test.yaml

@@ -354,6 +354,14 @@ jobs:
 
         echo "${HOME}/.cargo/bin" >> $GITHUB_PATH
 
+        '
+    - name: Install Rust toolchain
+      run: '# Set the default toolchain. Installs the toolchain if it is not already installed.
+
+        rustup default 1.82.0
+
+        cargo version
+
         '
     - name: Expose Pythons
       run: 'echo "/opt/python/cp37-cp37m/bin" >> $GITHUB_PATH
@@ -418,6 +426,14 @@ jobs:
 
         echo "${HOME}/.cargo/bin" >> $GITHUB_PATH
 
+        '
+    - name: Install Rust toolchain
+      run: '# Set the default toolchain. Installs the toolchain if it is not already installed.
+
+        rustup default 1.82.0
+
+        cargo version
+
         '
     - name: Expose Pythons
       run: 'echo "/opt/python/cp37-cp37m/bin" >> $GITHUB_PATH

src/python/pants_release/generate_github_workflows.py

@@ -312,16 +312,28 @@ def rust_channel() -> str:
     return cast(str, rust_toolchain["toolchain"]["channel"])
 
 
-def install_rustup() -> Step:
-    return {
-        "name": "Install rustup",
-        "run": dedent(
-            """\
+def install_rustup() -> list[Step]:
+    return [
+        {
+            "name": "Install rustup",
+            "run": dedent(
+                """\
             curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -v -y --default-toolchain none
             echo "${HOME}/.cargo/bin" >> $GITHUB_PATH
             """
-        ),
-    }
+            ),
+        },
+        {
+            "name": "Install Rust toolchain",
+            "run": dedent(
+                f"""\
+            # Set the default toolchain. Installs the toolchain if it is not already installed.
+            rustup default {rust_channel()}
+            cargo version
+            """
+            ),
+        },
+    ]
 
 
 def install_pythons(versions: list[str]) -> Step:
@@ -832,7 +844,7 @@ def build_wheels_job(
     if container:
         initial_steps = [
             *checkout(containerized=True, ref=for_deploy_ref),
-            install_rustup(),
+            *install_rustup(),
             {
                 "name": "Expose Pythons",
                 "run": dedent(