Revert syntax; add missing environment vars

.drone.yml

@@ -15,8 +15,10 @@ steps:
   image: bv11-cr01.bessems.eu/proxy/alpine/git
   commands:
   - git clone https://github.com/containers/skopeo.git .
-  - git checkout tags/$${SKOPEO_VERSION}
+  - git checkout tags/$SKOPEO_VERSION
   # - git checkout tags/v1.9.1
+  environment:
+    SKOPEO_VERSION: v1.9.1
 - name: Build binary
   image: bv11-cr01.bessems.eu/proxy/library/golang
   commands:
@@ -28,9 +30,9 @@ steps:
   - bin/skopeo --version
   - |
     curl \
-      --header "Authorization: token $${GIT_APIKEY}"
+      --header "Authorization: token $GIT_APIKEY"
       --upload-file bin/skopeo \
-      https://code.spamasaurus.com/api/packages/$${GIT_USERNAME}/generic/skopeo/$${SKOPEO_VERSION}/skopeo
+      https://code.spamasaurus.com/api/packages/$GIT_USERNAME/generic/skopeo/$SKOPEO_VERSION/skopeo
   # - cp bin/skopeo /output
   environment:
     CGO_ENABLED: 0