docc validation needs JAVA_HOME to be set up

Author: ktoso

.github/workflows/pull_request.yml

@@ -13,6 +13,8 @@ jobs:
       # FIXME: Something is off with the format task and it gets "stuck", need to investigate
       format_check_enabled: false
       license_header_check_project_name: Swift.org
+      # Because docc validation needs to build the project, and therefore needs JAVA_HOME to be set-up correctly
+      linux_pre_build_command: chmod +x ./.github/actions/prepare_env && ./.github/actions/prepare_env
 
   test-java:
     name: Test (Java) (${{ matrix.os_version }} swift:${{ matrix.swift_version }} jdk:${{matrix.jdk_vendor}})