➕ Add platform check Dockerfile

slides/containers/Buildkit.md

@@ -325,6 +325,29 @@ class: extra-details
 
 ---
 
+## Checking runtime capabilities
+
+Build and run the following Dockerfile:
+
+```dockerfile
+FROM --platform=linux/amd64 busybox AS amd64
+FROM --platform=linux/arm64 busybox AS arm64
+FROM --platform=linux/arm/v7 busybox AS arm32
+FROM --platform=linux/386 busybox AS ia32
+FROM alpine
+RUN apk add file
+WORKDIR /root
+COPY --from=amd64 /bin/busybox /root/amd64/busybox
+COPY --from=arm64 /bin/busybox /root/arm64/busybox
+COPY --from=arm32 /bin/busybox /root/arm32/busybox
+COPY --from=ia32 /bin/busybox /root/ia32/busybox
+CMD for A in *; do echo "$A => $($A/busybox uname -a)"; done
+```
+
+It will indicate which executables can be run on your engine.
+
+---
+
 ## More than builds
 
 - Buildkit is also used in other systems: