force use of bash to allow for non-posix user shells

src/nixos-anywhere.sh

@@ -283,7 +283,7 @@ done
 import_facts() {
   local facts filtered_facts
   if ! facts=$(
-    ssh_ -o ConnectTimeout=10 -- <<SSH
+    ssh_ -o ConnectTimeout=10 bash -- <<SSH
 set -efu ${enable_debug}
 has(){
   command -v "\$1" >/dev/null && echo "y" || echo "n"
@@ -347,7 +347,7 @@ if [[ ${is_kexec-n} == "n" ]] && [[ ${is_installer-n} == "n" ]]; then
   fi
 
   step Switching system into kexec
-  ssh_ <<SSH
+  ssh_ bash <<SSH
 set -efu ${enable_debug}
 $maybe_sudo rm -rf /root/kexec
 $maybe_sudo mkdir -p /root/kexec
@@ -436,7 +436,7 @@ if [[ -n ${extra_files-} ]]; then
 fi
 
 step Installing NixOS
-ssh_ <<SSH
+ssh_ bash <<SSH
 set -efu ${enable_debug}
 # when running not in nixos we might miss this directory, but it's needed in the nixos chroot during installation
 export PATH=\$PATH:/run/current-system/sw/bin