Added GTK3 install to test pipeline

.drone.yml

@@ -6,6 +6,7 @@ steps:
 - name: test
   image: rust:latest
   commands:
+  - apk install gtk+3.0-dev
   - rustup component add clippy
   - cargo clippy
   - cargo test --all
@@ -42,3 +43,9 @@ steps:
   - mc alias set fivesigma https://objects.5sigma.io $MINIOID $MINIOSECRET
   - cargo build --release --target=x86_64-pc-windows-msvc
   - mc cp target\x86_64-pc-windows-msvc\release\abacus-ui.exe fivesigma/public/abacus/abacus.exe
+  when:
+    event:
+      - promote
+    target:
+      - staging
+      - production