CI: Add ARM builder

Do a ZFS build inside of an ARM runner.  This only does a simple
build, it does not run the test suite.  The build runs on the
runner itself rather than in a VM, since nesting is not supported on
Github ARM runners.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: George Melikov <mail@gmelikov.ru>
Signed-off-by: Tony Hutter <hutter2@llnl.gov>
Closes #18343

.github/workflows/scripts/qemu-3-deps-vm.sh

@@ -3,8 +3,11 @@
 ######################################################################
 # 3) install dependencies for compiling and loading
 #
-# $1: OS name (like 'fedora41')
-# $2: (optional) Experimental Fedora kernel version, like "6.14" to
+# qemu-3-deps-vm.sh [--poweroff] OS_NAME [FEDORA_VERSION]
+#
+# --poweroff: Power off the VM after installing dependencies
+# OS_NAME: OS name (like 'fedora41')
+# FEDORA_VERSION: (optional) Experimental Fedora kernel version, like "6.14" to
 #     install instead of Fedora defaults.
 ######################################################################
 
@@ -153,6 +156,12 @@ function install_fedora_experimental_kernel {
   sudo dnf -y copr disable @kernel-vanilla/mainline
 }
 
+POWEROFF=""
+if [ "$1" == "--poweroff" ] ; then
+        POWEROFF=1
+        shift
+fi
+
 # Install dependencies
 case "$1" in
   almalinux8)
@@ -212,6 +221,11 @@ case "$1" in
     sudo apt-get install -yq linux-tools-common libtirpc-dev \
       linux-modules-extra-$(uname -r)
     sudo apt-get install -yq dh-sequence-dkms
+
+    # Need 'build-essential' explicitly for ARM builder
+    # https://github.com/actions/runner-images/issues/9946
+    sudo apt-get install -yq build-essential
+
     echo "##[endgroup]"
     echo "##[group]Delete Ubuntu OpenZFS modules"
     for i in $(find /lib/modules -name zfs -type d); do sudo rm -rvf $i; done
@@ -306,5 +320,7 @@ esac
 
 # reset cloud-init configuration and poweroff
 sudo cloud-init clean --logs
-sleep 2 && sudo poweroff &
+if [ "$POWEROFF" == "1" ] ; then
+        sleep 2 && sudo poweroff &
+fi
 exit 0

.github/workflows/scripts/qemu-4-build-vm.sh

@@ -350,7 +350,16 @@ fi
 # save some sysinfo
 uname -a > /var/tmp/uname.txt
 
-cd $HOME/zfs
+# Check if we're running this script from within a VM or on the runner itself.
+# Most of the time we will be running in a VM, but the ARM builder actually
+# runs this script on the runner.  If we happen to be running on the ARM
+# runner, we will start in the ZFS source directory.  If we're running on a VM
+# then we'll just start in our home directory, and will need to 'cd' into our
+# source directory.
+if [ ! -e META ] ; then
+  cd $HOME/zfs
+fi
+
 export PATH="$PATH:/sbin:/usr/sbin:/usr/local/sbin"
 
 extra=""