chore(ci): modernize config

.woodpecker/build.yml

@@ -3,19 +3,20 @@ matrix:
     - 'amd64'
     - 'arm64'
 
-platform: "linux/${ARCH}"
+labels:
+  platform: "linux/${ARCH}"
 
-branches:
-  exclude: [main]
+when:
+  branch:
+    exclude: [main]
+  event: push
 
-pipeline:
+steps:
   build:
-    image: 'rust:1.70-alpine3.18'
+    image: 'rust:1.71-alpine3.18'
     commands:
       - apk add --no-cache build-base
       - cargo build --verbose
       - cargo test --verbose
       # Binaries, even debug ones, should be statically compiled
       - '[ "$(readelf -d target/debug/alex | grep NEEDED | wc -l)" = 0 ]'
-    when:
-      event: [push]