Clean apt package cache ASAP to safe some disk space

Author: tnull

.github/workflows/build.yml

@@ -49,10 +49,12 @@ jobs:
         run: |
           rustup target add thumbv7m-none-eabi
           sudo apt-get -y install gcc-arm-none-eabi
+          sudo apt-get clean
       - name: shellcheck the CI and `contrib` scripts
         if: "matrix.platform == 'ubuntu-latest'"
         run: |
           sudo apt-get -y install shellcheck
+          sudo apt-get clean
           shellcheck ci/*.sh -aP ci
           shellcheck contrib/*.sh -aP contrib
       - name: Set RUSTFLAGS to deny warnings
@@ -260,6 +262,7 @@ jobs:
         run: |
           sudo apt-get update
           sudo apt-get -y install build-essential binutils-dev libunwind-dev
+          sudo apt-get clean
       - name: Pin the regex dependency
         run: |
           cd fuzz && cargo update -p regex --precise "1.9.6" --verbose