build: Drop aarch64 cross-build

This has been lagging behind on an older Rust version and we have
enough coverage from our Jenkins CI agent.

Signed-off-by: Rob Bradford <robert.bradford@intel.com>

.github/workflows/cross-build.yaml

@@ -1,32 +0,0 @@
-name: Cloud Hypervisor Cross Build
-on: [pull_request, create]
-
-jobs:
-  build:
-    if: github.event_name == 'pull_request'
-    name: Build
-    runs-on: ubuntu-latest
-    strategy:
-      matrix:
-        rust:
-          - 1.46.0
-        target:
-          - aarch64-unknown-linux-gnu
-          - aarch64-unknown-linux-musl
-    steps:
-      - name: Code checkout
-        uses: actions/checkout@v2
-      - name: Install Rust toolchain (${{ matrix.rust }})
-        uses: actions-rs/toolchain@v1
-        with:
-            toolchain: ${{ matrix.rust }}
-            target: ${{ matrix.target }}
-            override: true
-      - name: Install arm64 libfdt
-        run: wget http://ftp.us.debian.org/debian/pool/main/d/device-tree-compiler/libfdt-dev_1.6.0-1_arm64.deb && dpkg-deb -xv libfdt-dev_1.6.0-1_arm64.deb ./tlibfdtdev && mkdir -p target/debug/deps &&  cp ./tlibfdtdev/usr/lib/aarch64-linux-gnu/libfdt.a target/debug/deps/ && echo "libfdt copied into build tree"
-      - name: Build
-        uses: actions-rs/cargo@v1
-        with:
-          use-cross: true
-          command: build
-          args: --target=${{ matrix.target }} --no-default-features --features "kvm"

.github/workflows/quality-aarch64.yaml

@@ -23,7 +23,7 @@ jobs:
             override: true
             components: rustfmt, clippy
       - name: Install arm64 libfdt
-        run: wget http://ftp.us.debian.org/debian/pool/main/d/device-tree-compiler/libfdt-dev_1.6.0-1_arm64.deb && dpkg-deb -xv libfdt-dev_1.6.0-1_arm64.deb ./tlibfdtdev && sudo mkdir /tmmmp && mkdir target && mkdir target/debug && mkdir target/debug/deps && sudo cp ./tlibfdtdev/usr/lib/aarch64-linux-gnu/libfdt.a target/debug/deps/libfdt.a && echo "libfdt installed"
+        run: wget http://ftp.us.debian.org/debian/pool/main/d/device-tree-compiler/libfdt-dev_1.6.0-1_arm64.deb && dpkg-deb -xv libfdt-dev_1.6.0-1_arm64.deb ./tlibfdtdev && mkdir -p target/debug/deps && sudo cp ./tlibfdtdev/usr/lib/aarch64-linux-gnu/libfdt.a target/debug/deps/libfdt.a && echo "libfdt installed"
       - name: Formatting (rustfmt)
         run: cargo fmt -- --check
       - name: Clippy (kvm)