get python on the build CI image

Author: tobz

.ci/images/build/Dockerfile

@@ -10,7 +10,8 @@ ARG TARGETARCH
 
 # Install the basics for building and compiling software projects.
 RUN apt-get update && \
-    apt-get install -y --no-install-recommends build-essential software-properties-common curl ca-certificates git gnupg2 lsb-release make cmake unzip gcc g++ binutils jq bc bzip2 ninja-build && \
+    apt-get install -y --no-install-recommends build-essential software-properties-common curl ca-certificates git gnupg2 \
+    lsb-release make cmake unzip gcc g++ binutils jq bc bzip2 ninja-build python3 python3-pip && \
     apt-get clean
 
 # Install Go, which we need to build AWS-LC in FIPS-compliant mode.