Work around cargo crate index fetch error rust-lang/cargo#10303.

Set `CARGO_NET_GIT_FETCH_WITH_CLI` for rust 1.43.0. New versions do not
have the issue and can continue to use libgit2 to fetch the crate index.

.github/workflows/ci-min-test-matrix.yml

@@ -23,6 +23,14 @@ jobs:
         exclude:
           - os: ubuntu-latest
             rust: stable
+        include: # https://github.com/rust-lang/cargo/issues/10303
+          - cli_fetch: false
+          - os: ubuntu-latest
+            rust: 1.43.0
+            cli_fetch: true
+          - os: macOS-latest
+            rust: 1.43.0
+            cli_fetch: true
 
     steps:
       - name: Checkout repository
@@ -43,3 +51,5 @@ jobs:
         with:
           command: test
           args: --all --verbose --features "use_serde"
+          env:
+            CARGO_NET_GIT_FETCH_WITH_CLI: ${{ cli_fetch }}