Update Python 3 in Docker image to 3.10 (#100)

Otherwise `apt` will install some other bs LMAO 

---------

Co-authored-by: Natsu Kagami <[email protected]>

docker/Dockerfile

@@ -1,7 +1,21 @@
+# Stage -1: Update apt-get
+FROM ubuntu:jammy AS base-ubuntu
+
+# Mount apt's cache folders to cache install but maintain
+# reproducibility on local machines. More details at:
+# https://github.com/moby/buildkit/blob/master/frontend/dockerfile/docs/reference.md#run---mounttypecache
+
+# Set sharing=locked to avoid race condition with between stages.
+RUN --mount=type=cache,target=/var/cache/apt,sharing=locked \
+    --mount=type=cache,target=/var/lib/apt,sharing=locked \
+    apt-get update && apt-get upgrade -y
+
 # Stage 0: Compile isolate
-FROM ubuntu:jammy AS isolate
+FROM base-ubuntu AS isolate
 
-RUN apt-get update && apt-get install -y libcap-dev gcc git make
+RUN --mount=type=cache,target=/var/cache/apt,sharing=locked \
+    --mount=type=cache,target=/var/lib/apt,sharing=locked \
+    apt-get update && apt-get install -y libcap-dev gcc git make
 
 WORKDIR /isolate
 
@@ -37,11 +51,14 @@ RUN scripts/install_tools.sh
 RUN go generate && go build -tags production -o kjudge cmd/kjudge/main.go
 
 # Stage 3: Create awesome output image
-FROM ubuntu:jammy
+FROM base-ubuntu
 
-RUN apt-get update && DEBIAN_FRONTEND="noninteractive" TZ="Asia/Ho_Chi_Minh" apt-get install -y \
-    build-essential openjdk-11-jdk-headless fp-compiler python3.6 cgroup-lite python2.7 rustc golang libcap-dev # Compilers  \
-    openssl # For HTTPS support
+RUN --mount=type=cache,target=/var/cache/apt,sharing=locked \
+    --mount=type=cache,target=/var/lib/apt,sharing=locked \
+    apt-get update && DEBIAN_FRONTEND="noninteractive" TZ="Asia/Ho_Chi_Minh" apt-get install -y \
+    build-essential openjdk-11-jdk-headless fp-compiler cgroup-lite \
+    python3.10 python2.7 rustc golang libcap-dev \
+    openssl
 
 COPY --from=isolate /isolate/ /isolate
 
@@ -59,4 +76,3 @@ EXPOSE 80 443
 
 WORKDIR /
 ENTRYPOINT ["scripts/start_container.sh"]
-