Use nix to do builds

.gitlab-ci-build.yml.in

@@ -31,19 +31,8 @@ stages:
     PACKER_CONFIG_DIR: ./packer_config/
     PACKER_CACHE_DIR: ./cache/
     PACKER_LOG: 1
-    COMMAND: >
-      packer build ${only}
-      -var-file="${distro}"
-      -var build=${BUILD}
-      -var cpus=2
-      -var memory=4096
-      ${EXCEPT}
-      sources
   script:
-    - find "${PACKER_CONFIG_DIR}" -name '*_linux_amd64' -exec chmod +x '{}' ";"
-    - packer init sources
-    - echo $COMMAND > build.sh
-    - bash build.sh || exit 1
+    - nix run ".#${buildcmd}" || exit 1
 
 qemu.amd64:
   extends: .build
@@ -69,6 +58,14 @@ hyperv-iso.amd64:
     <<: *variables
     only: '-only="hyperv-iso.amd64"'
     tag: hyperv
+    COMMAND: >
+      packer build ${only}
+      -var-file="${distro}"
+      -var build=${BUILD}
+      -var cpus=2
+      -var memory=4096
+      ${EXCEPT}
+      sources
   parallel:
     matrix: HYPERV_MATRIX
   script: