docs: add note for building sample on ARM (#1209)

Author: deki

samples/springboot3/pet-store-native/Dockerfile

@@ -8,7 +8,8 @@ RUN yum -y update \
 
 # Graal VM
 ENV GRAAL_VERSION 21.0.2
-ENV GRAAL_FILENAME graalvm-community-jdk-${GRAAL_VERSION}_linux-x64_bin.tar.gz
+ENV ARCHITECTURE x64
+ENV GRAAL_FILENAME graalvm-community-jdk-${GRAAL_VERSION}_linux-${ARCHITECTURE}_bin.tar.gz
 RUN curl -4 -L https://github.com/graalvm/graalvm-ce-builds/releases/download/jdk-${GRAAL_VERSION}/${GRAAL_FILENAME} | tar -xvz
 RUN mv graalvm-community-openjdk-${GRAAL_VERSION}* /usr/lib/graalvm
 ENV JAVA_HOME /usr/lib/graalvm

samples/springboot3/pet-store-native/README.md

@@ -5,6 +5,10 @@ In this sample, you'll build a native GraalVM image for running web workloads in
 
 You first need to build the function, then you will deploy it to AWS Lambda.
 
+Please note that the sample is for `x86` architectures. In case you want to build and run it on ARM, e.g. Apple Mac M1, M2, ... 
+you must change the according line in the `Dockerfile` to `ENV ARCHITECTURE aarch64`. 
+In addition, uncomment the `arm64` Architectures section in `template.yml`.
+
 ### Step 1 - Build the native image
 
 Before starting the build, you must clone or download the code in **pet-store-native**.