ci: anchor rust-toolchain channel grep so it ignores comments

Author: emmanuel-keller

.github/workflows/cross.yml

@@ -45,7 +45,7 @@ jobs:
 
       - name: Read Rust toolchain version
         id: rust-version
-        run: echo "CHANNEL=$(grep 'channel' rust-toolchain.toml | sed 's/.*"\(.*\)"/\1/')" >> $GITHUB_OUTPUT
+        run: echo "CHANNEL=$(grep '^channel' rust-toolchain.toml | sed 's/.*"\(.*\)"/\1/')" >> $GITHUB_OUTPUT
 
       - name: Set up Rust
         uses: dtolnay/rust-toolchain@631a55b12751854ce901bb631d5902ceb48146f7 # stable
@@ -98,7 +98,7 @@ jobs:
 
       - name: Read Rust toolchain version
         id: rust-version
-        run: echo "CHANNEL=$(grep 'channel' rust-toolchain.toml | sed 's/.*"\(.*\)"/\1/')" >> $GITHUB_OUTPUT
+        run: echo "CHANNEL=$(grep '^channel' rust-toolchain.toml | sed 's/.*"\(.*\)"/\1/')" >> $GITHUB_OUTPUT
 
       - name: Set up Rust
         uses: dtolnay/rust-toolchain@631a55b12751854ce901bb631d5902ceb48146f7 # stable
@@ -132,7 +132,7 @@ jobs:
       - name: Read Rust toolchain version
         id: rust-version
         shell: bash
-        run: echo "CHANNEL=$(grep 'channel' rust-toolchain.toml | sed 's/.*"\(.*\)"/\1/')" >> $GITHUB_OUTPUT
+        run: echo "CHANNEL=$(grep '^channel' rust-toolchain.toml | sed 's/.*"\(.*\)"/\1/')" >> $GITHUB_OUTPUT
 
       - name: Set up Rust
         uses: dtolnay/rust-toolchain@631a55b12751854ce901bb631d5902ceb48146f7 # stable
@@ -167,7 +167,7 @@ jobs:
 
       - name: Read Rust toolchain version
         id: rust-version
-        run: echo "CHANNEL=$(grep 'channel' rust-toolchain.toml | sed 's/.*"\(.*\)"/\1/')" >> $GITHUB_OUTPUT
+        run: echo "CHANNEL=$(grep '^channel' rust-toolchain.toml | sed 's/.*"\(.*\)"/\1/')" >> $GITHUB_OUTPUT
 
       - name: Set up Rust
         uses: dtolnay/rust-toolchain@631a55b12751854ce901bb631d5902ceb48146f7 # stable