Consistently use backslash directories on Windows

Author: dtolnay

action.yml

@@ -63,14 +63,14 @@ runs:
 
     - run: |
         : set $CARGO_HOME
-        echo CARGO_HOME=${CARGO_HOME:-${{runner.os == 'Windows' && '$USERPROFILE' || '$HOME'}}/.cargo} >> $GITHUB_ENV
+        echo CARGO_HOME=${CARGO_HOME:-'${{runner.os == 'Windows' && '$USERPROFILE\.cargo' || '$HOME/.cargo'}}'} >> $GITHUB_ENV
       shell: bash
 
     - run: |
         : install rustup if needed
         if ! command -v rustup &>/dev/null; then
           curl --proto '=https' --tlsv1.2 --retry 10 --retry-connrefused --location --silent --show-error --fail https://sh.rustup.rs | sh -s -- --default-toolchain none -y
-          echo "$CARGO_HOME/bin" >> $GITHUB_PATH
+          echo '$CARGO_HOME/bin' >> $GITHUB_PATH
         fi
       if: runner.os != 'Windows'
       shell: bash
@@ -80,7 +80,7 @@ runs:
         if ! command -v rustup &>/dev/null; then
           curl --proto '=https' --tlsv1.2 --retry 10 --retry-connrefused --location --silent --show-error --fail https://static.rust-lang.org/rustup/dist/${{ runner.arch == 'ARM64' && 'aarch64' || 'x86_64' }}-pc-windows-msvc/rustup-init.exe --output '${{runner.temp}}\rustup-init.exe'
           '${{runner.temp}}\rustup-init.exe' --default-toolchain none --no-modify-path -y
-          echo "$USERPROFILE/.cargo/bin" >> $GITHUB_PATH
+          echo '$USERPROFILE\.cargo\bin' >> $GITHUB_PATH
         fi
       if: runner.os == 'Windows'
       shell: bash