fix: Ensure latest Alpine packages are used

Dockerfile

@@ -7,13 +7,15 @@ ARG DISTRO_VERSION="3.15"
 # Grab a fresh copy of the image and install GCC
 FROM python:${RUNTIME_VERSION}-alpine${DISTRO_VERSION} AS python-alpine
 # Install GCC (Alpine uses musl but we compile and link dependencies with GCC)
-RUN apk add --no-cache \
+RUN apk upgrade -U --available --no-cache && \
+    apk add --no-cache \
     libstdc++
 
 # Stage 2 - build function and dependencies
 FROM python-alpine AS build-image
 # Install aws-lambda-cpp build dependencies
-RUN apk add --no-cache \
+RUN apk upgrade -U --available --no-cache && \
+    apk add --no-cache \
     build-base \
     libtool \
     autoconf \