Faster Windows builds in CircleCI

We already test the build implicitly when running the test, no need for
a separate build that takes 6 minutes.

We already run clippy in the Linux environment. It's not worth another 6
minutes on each build to run it again in Windows.

There was a hack in the Clippy installer to get cargo git checkouts
working in CircleCI. Since that's removed, we revisited the hack, and
the cleaner workaround of using .cargo/config was put in place.

For more, see: rust-lang/cargo#2078

.cargo/config

@@ -0,0 +1,2 @@
+[net]
+git-fetch-with-cli = true

.circleci/config.yml

@@ -69,18 +69,6 @@ jobs:
       - run:
           name: Install target toolchain
           command: rustup toolchain install stable-x86_64-pc-windows-msvc
-      - run:
-          name: Install Clippy
-          command: rustup component add clippy
-      - run:
-          name: Run Clippy
-          # Remove the first two lines of gitconfig as work around
-          command: |
-            (gc ..\.gitconfig | select -Skip 2) | sc ..\.gitconfig
-            cargo clippy --package trin -- --deny warnings
-      - run:
-          name: Cargo Build --target x86_64-pc-windows-msvc
-          command: cargo build --target x86_64-pc-windows-msvc
       - run:
           name: Cargo Test --target x86_64-pc-windows-msvc
           command: cargo test --target x86_64-pc-windows-msvc