Update microypthon binary to 1.15

tools/Dockerfile

@@ -0,0 +1,25 @@
+FROM ubuntu:latest
+
+ARG DEBIAN_FRONTEND=noninteractive
+
+RUN apt-get update && \
+    apt-get install -y build-essential libffi-dev git pkg-config python python3 && \
+    rm -rf /var/lib/apt/lists/* && \
+    git clone https://github.com/micropython/micropython.git && \
+    cd micropython && \
+    git checkout v1.15 && \
+    git submodule update --init && \
+    cd mpy-cross && \
+    make && \
+    cd .. && \
+    cd ports/unix && \
+    make axtls && \
+    make && \
+    make test && \
+    make install && \
+    apt-get purge --auto-remove -y  build-essential libffi-dev git pkg-config python python3 && \
+    cd ../../.. && \
+    rm -rf micropython
+
+CMD ["/usr/local/bin/micropython"]
+

tools/update-micropython.sh

@@ -0,0 +1,6 @@
+# this script updates the micropython binary in the /bin directory that is
+# used to run unit tests under GitHub Actions builds
+docker build -t micropython .
+docker create -it --name dummy-micropython micropython
+docker cp dummy-micropython:/usr/local/bin/micropython ../bin/micropython
+docker rm dummy-micropython