build.sh: Warn user of unsupported build environment architecture and fail early if binfmt_misc isn't working as expected

Dockerfile

@@ -8,7 +8,7 @@ RUN apt-get -y update && \
         git vim parted \
         quilt coreutils qemu-user-static debootstrap zerofree zip dosfstools \
         libarchive-tools libcap2-bin rsync grep udev xz-utils curl xxd file kmod bc \
-        binfmt-support ca-certificates fdisk gpg pigz\
+        binfmt-support ca-certificates fdisk gpg pigz arch-test \
     && rm -rf /var/lib/apt/lists/*
 
 COPY . /pi-gen/

README.md

@@ -19,7 +19,7 @@ To install the required dependencies for `pi-gen` you should run:
 ```bash
 apt-get install coreutils quilt parted qemu-user-static debootstrap zerofree zip \
 dosfstools libarchive-tools libcap2-bin grep rsync xz-utils file git curl bc \
-gpg pigz xxd
+gpg pigz xxd arch-test
 ```
 
 The file `depends` contains a list of tools needed.  The format of this

build.sh

@@ -244,6 +244,15 @@ fi
 
 dependencies_check "${BASE_DIR}/depends"
 
+echo "Checking native $ARCH executable support..."
+if ! arch-test -n "$ARCH"; then
+	echo "WARNING: Only a native build environment is supported. Checking emulated support..."
+	if ! arch-test "$ARCH"; then
+		echo "No fallback mechanism found. Ensure your OS has binfmt_misc support enabled and configured."
+		exit 1
+	fi
+fi
+
 #check username is valid
 if [[ ! "$FIRST_USER_NAME" =~ ^[a-z][-a-z0-9_]*$ ]]; then
 	echo "Invalid FIRST_USER_NAME: $FIRST_USER_NAME"

depends

@@ -19,3 +19,4 @@ lsmod:kmod
 bc
 gpg
 pigz
+arch-test