ci: set DISABLE_WARN_OUTSIDE_CONTAINER=1 for CodeQL action

CodeQL autobuild uses the makefile, but outside of a container, so let's
set this variable to prevent it having to wait 10 seconds;

    Use "make dev" to start an interactive development container,
    use "make -f docker.Makefile " to execute this target
    in a container, or set DISABLE_WARN_OUTSIDE_CONTAINER=1 to
    disable this warning.

    Press Ctrl+C now to abort, or wait for the script to continue..

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

.github/workflows/codeql.yml

@@ -26,6 +26,8 @@ jobs:
   codeql:
     runs-on: 'ubuntu-latest'
     timeout-minutes: 360
+    env:
+      DISABLE_WARN_OUTSIDE_CONTAINER: '1'
     permissions:
       actions: read
       contents: read