build-test: Move system package installation to ci-install.sh

It's more maintainable to have the system packages listed in
ci-install.sh instead of in build-test.yaml.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

.github/workflows/build-test.yaml

@@ -8,9 +8,6 @@ jobs:
     steps:
     - uses: actions/checkout@v2
 
-    - name: Install system dependencies
-      run: sudo apt-get install gcc-avr avr-libc pv libmpfr-dev libgmp-dev libmpc-dev texinfo libncurses5-dev bison flex python-virtualenv virtualenv python-dev libffi-dev build-essential libnewlib-arm-none-eabi gcc-arm-none-eabi binutils-arm-none-eabi
-
     - name: Setup cache
       uses: actions/cache@v2
       with: