CI: Purge pleroma build directory between runs

.gitlab-ci.yml

@@ -24,6 +24,7 @@ stages:
   - docker
 
 before_script:
+  - rm -rf _build/*/lib/pleroma
   - apt-get update && apt-get install -y cmake
   - mix local.hex --force
   - mix local.rebar --force
@@ -31,6 +32,9 @@ before_script:
   - apt-get -qq update
   - apt-get install -y libmagic-dev
 
+after_script:
+  - rm -rf _build/*/lib/pleroma
+
 build:
   stage: build
   script: