Add workflow and add libopencm3 as submodule

.github/workflows/build.yml

@@ -0,0 +1,15 @@
+name: Build CI
+
+on: [push, pull_request]
+
+jobs:
+  makefile-build:
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+    steps:
+    - uses: actions/checkout@v3
+    - name: Install Dependencies
+      run: sudo apt-get update && sudo apt-get install -y build-essential make arm-none-eabi-gdb  binutils-arm-none-eabi libnewlib-arm-none-eabi
+    - name: Build
+      run: git submodule update --init && cd libopencm3 && make && cd ../ && mkdir build && cd build && cmake ../ && make

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "libopencm3"]
+	path = libopencm3
+	url = https://github.com/libopencm3/libopencm3

config.cmake

@@ -1,5 +1,5 @@
 # Always declare this before stm32-toolchain.cmake
 #
 set(MCU STM32F1)
-set(LIBOPENCM3_DIR "/home/ami/repos/libopencm3")
+set(LIBOPENCM3_DIR "./libopencm3")
 set(SERIAL_PORT "/dev/ttyUSB0")