WIP: crossbuilds will detect if we are trying to build from a arm64 host and echo a message to the user

Author: marc-casavant

scripts/docker/crossbuild.mk

@@ -8,6 +8,8 @@ crossbuild crossbuild.help :
 	@echo crossbuild requires Docker to be installed
 else
 
+UNAME_M := $(shell uname -m)
+
 #
 #  Short list of common builds
 #
@@ -38,6 +40,17 @@ CB_PROF_CPREFIX:=fr40x-prof-
 # List of profiling images (only directories that contain a Dockerfile.cb)
 CB_PROF_IMAGES:=$(sort $(patsubst $(PT)/%/Dockerfile.cb,%,$(wildcard $(PT)/*/Dockerfile.cb)))
 
+#
+#  Building from arm64 is not supported. Check if a build target was requested.
+#
+ifneq (,$(filter $(UNAME_M),arm64 aarch64))
+_CB_BUILD_TARGETS := crossbuild crossbuild.common crossbuild.prof \
+    $(foreach IMG,$(CB_IMAGES),crossbuild.$(IMG)) \
+    $(foreach IMG,$(CB_PROF_IMAGES),crossbuild.$(IMG).prof)
+ifneq (,$(filter $(_CB_BUILD_TARGETS),$(MAKECMDGOALS)))
+$(error Building from arm64 is currently not supported)
+endif
+endif
 
 # Location of the .git dir (may be different for e.g. submodules)
 GITDIR:=$(shell perl -MCwd -e 'print Cwd::abs_path shift' $$(git rev-parse --git-dir))