flake: Create TMP dir and use it for $HOME PATH

flake.nix

@@ -19,7 +19,8 @@
 
             buildPhase = ''
               # kicad-cli requires the use of $HOME
-              export HOME=/tmp
+              TMP_DIR="$(pwd)/$(mktemp -d tmp.XXXX)"
+              export HOME=$TMP_DIR
 
               if [ "${variant}" != "copper_plate" ]; then
                 SCH=kirdy_LD_adapter_${variant}.kicad_sch
@@ -56,6 +57,7 @@
                 export KICAD7_3DMODEL_DIR=${pkgs.kicad.libraries.packages3d}/share/kicad/3dmodels
                 kicad-cli pcb export step $PCB --subst-models --force -o $PREFIX.step
               fi
+              rm -r $TMP_DIR
             '';
 
             installPhase = ''