Raise minimum tested compiler to 1.70

Required by the `toml` crate.

.github/workflows/ci.yml

@@ -26,6 +26,7 @@ jobs:
           - rust: beta
           - rust: stable
           - rust: 1.60.0
+          - rust: 1.70.0
           - rust: 1.74.0
           - name: Cargo on macOS
             rust: nightly
@@ -56,13 +57,14 @@ jobs:
         # builds.
         run: |
           echo RUSTFLAGS=$RUSTFLAGS >> $GITHUB_ENV
-          echo exclude=--exclude cxx-test-suite ${{matrix.rust == '1.60.0' && '--exclude cxxbridge-cmd' || ''}} >> $GITHUB_OUTPUT
+          echo exclude=--exclude cxx-test-suite ${{matrix.rust == '1.70.0' && '--exclude cxxbridge-cmd' || ''}} >> $GITHUB_OUTPUT
         env:
           RUSTFLAGS: ${{env.RUSTFLAGS}} ${{matrix.os && github.event_name != 'schedule' && '--cfg skip_ui_tests' || ''}}
         id: testsuite
         shell: bash
       - run: cargo run --manifest-path demo/Cargo.toml
       - run: cargo test --workspace ${{steps.testsuite.outputs.exclude}}
+        if: matrix.rust != '1.60.0'
       - run: cargo check --no-default-features --features alloc
         env:
           RUSTFLAGS: --cfg compile_error_if_std ${{env.RUSTFLAGS}}