docker: Support building for multiple architectures
Add instructions on how to build the file for multiple architectures.
Add a message indicating what is happening.
Update the documentation as well.
Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/tools/docker/Dockerfile b/tools/docker/Dockerfile
index bc8d1eb..43cd370 100644
--- a/tools/docker/Dockerfile
+++ b/tools/docker/Dockerfile
@@ -6,9 +6,18 @@
LABEL org.opencontainers.image.authors="Tom Rini <trini@konsulko.com>"
LABEL org.opencontainers.image.description=" This image is for building U-Boot inside a container"
+# Used by docker to set the target platform: valid values are linux/arm64/v8
+# and linux/amd64
+ARG TARGETPLATFORM
+
+# Used by docker to set the build platform: the only valid value is linux/amd64
+ARG BUILDPLATFORM
+
# Make sure apt is happy
ENV DEBIAN_FRONTEND=noninteractive
+RUN echo "Building on $BUILDPLATFORM, for target $TARGETPLATFORM"
+
# Add LLVM repository
RUN --mount=type=cache,target=/var/cache/apt,sharing=locked \
--mount=type=cache,target=/var/lib/apt,sharing=locked \