ci: move one test job to arm64 to allow parallel execution

.woodpecker/test.yml

@@ -1,6 +1,3 @@
-labels:
-  platform: linux/amd64
-
 when:
   - event: pull_request
 
@@ -10,9 +7,14 @@ matrix:
     - ELIXIR_VERSION: 1.14
       OTP_VERSION: 25
       LINT: NO
+      PLATFORM: linux/amd64
     - ELIXIR_VERSION: 1.18
       OTP_VERSION: 27
       LINT: YES
+      PLATFORM: linux/arm64
+
+labels:
+  platform: ${PLATFORM}
 
 services:
   postgres:
@@ -33,6 +35,7 @@ steps:
       DB_HOST: postgres
       LINT: ${LINT}
     commands:
+      - sh -c 'uname -a && cat /etc/os-release || :'
       - mix local.hex --force
       - mix local.rebar --force
       - mix deps.get