ci: use cargo-ndk 2.12.7 for MSRV tests

With an MSRV of 1.64.0 we can use the latest cargo-ndk release in the
v2.12.x stream when doing our MSRV testing for the Android target. The
3.0.x and 3.1.x streams require a more aggressive MSRV than we can
support at this time.

Author: cpu

.github/workflows/ci.yml

@@ -75,7 +75,7 @@ jobs:
 
       - name: Install cargo-ndk.
         run: |
-          cargo install cargo-ndk
+          cargo install cargo-ndk --version 2.12.7
           rustup target add aarch64-linux-android
 
       - name: Clippy (${{ matrix.os }})