SWPROT-8953: build: Improve detection/setup of foreign arch like armhf

It was tested on github, the alternative would not to support arm images
provided by github.

For the record, native build on arm64 takes up to 5h on github.

Relate-to: https://medium.com/swlh/using-github-actions-to-build-arm-based-docker-images-413a8d498ee
Origin: #14
Signed-off-by: Philippe Coval <philippe.coval@silabs.com>

Author: rzr

scripts/build-rootfs.sh

@@ -16,8 +16,10 @@ EOF
 project="unifysdk"
 debian_suite="bookworm"
 
+debian_arch=$(dpkg --print-architecture)
+
 # Can be overloaded from env eg: ARCH=arm64"
-target_debian_arch=${ARCH:="$(dpkg --print-architecture)"}
+target_debian_arch=${ARCH:="${debian_arch}"}
 
 debian_mirror_url="http://deb.debian.org/debian"
 sudo="sudo"
@@ -27,45 +29,76 @@ MAKE="/usr/bin/make"
 CURDIR="$PWD"
 chroot="systemd-nspawn"
 packages="debootstrap \
-  binfmt-support \
   debian-archive-keyring \
-  qemu-user-static \
   systemd-container \
   time \
 "
 case $target_debian_arch in
     amd64)
+        qemu_system="qemu-system-${CMAKE_SYSTEM_PROCESSOR}"
         export CMAKE_SYSTEM_PROCESSOR="x86_64"
         export CARGO_TARGET_TRIPLE="${CMAKE_SYSTEM_PROCESSOR}-unknown-linux-gnu"
-        packages="${packages} qemu-system-x86"
-        qemu_system="qemu-system-${CMAKE_SYSTEM_PROCESSOR}"
+        qemu_package="qemu-system-x86"
         ;;
 
     arm64)
         qemu_arch="aarch64"
         qemu_system="qemu-system-${qemu_arch}"
         export CMAKE_SYSTEM_PROCESSOR="${qemu_arch}"
         export CARGO_TARGET_TRIPLE="${CMAKE_SYSTEM_PROCESSOR}-unknown-linux-gnu"
-        packages="${packages} qemu-system-arm"
+        qemu_package="qemu-system-arm"
         ;;
 
+    armhf)
+        debian_arch="armhf"
+        qemu_arch="arm"
+        qemu_system="qemu-system-${qemu_arch}"
+        export CMAKE_SYSTEM_PROCESSOR="armv7l"
+        export CARGO_TARGET_TRIPLE="armv7-unknown-linux-gnueabihf"
+        qemu_package="qemu-system-arm"
+
+        # Workaround: https://github.com/armbian/build/issues/5330
+        binfmt_file="/var/lib/binfmts/qemu-${qemu_arch}"
+        [ -e "$binfmt_file" ] || cat<<EOF \
+                | { sudo mkdir -p /var/lib/binfmts && sudo tee "$binfmt_file" ; }
+package qemu-user-static
+interpreter /usr/libexec/qemu-binfmt/arm-binfmt-P
+magic \x7f\x45\x4c\x46\x01\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x28\x00
+offset 0
+mask \xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff\xff
+credentials yes
+fix_binary no
+preserve yes
+EOF
+        ;;
     *)
         CMAKE_SYSTEM_PROCESSOR="$ARCH"
         CARGO_TARGET_TRIPLE="${CMAKE_SYSTEM_PROCESSOR}-unknown-linux-gnu"
         qemu_arch="${ARCH}"
         qemu_system="qemu-system-${qemu_arch}"
+        qemu_package="${qemu_system}"
         echo "error: Not supported yet"
 
         exit 1
         ;;
 esac
+qemu_file="/usr/bin/${qemu_system}"
+binfmt_file="/var/lib/binfmts/qemu-${qemu_arch}"
 
 ${sudo} apt-get update
 ${sudo} apt install -y ${packages}
-if [ -e "/var/lib/binfmts/qemu-${qemu_arch}" ]; then
-    ${sudo} update-binfmts --enable "qemu-${qemu_arch}"
+
+if [ "${debian_target_arch}" != "${debian_arch}" ] ; then
+    echo "log: ${ARCH}: Support foreign arch: ${qemu_arch}"
+    ${sudo} apt-get update
+    packages="binfmt-support qemu-user-static ${qemu_package}"
+    ${sudo} apt install -y ${packages}
+
+    if [ -e "${qemu_file}" ]; then
+        ${sudo} update-binfmts --enable "qemu-${qemu_arch}" \
+            || find /usr/libexec/qemu-binfmt/
+    fi
 fi
-qemu_file="/usr/bin/${qemu_system}"
 
 if [ ! -d "${rootfs_dir}" ] ; then
     ${sudo} mkdir -pv "${rootfs_dir}"