lineageos: add note about upstream CI build script

Author: danielfullmer

flavors/lineageos/default.nix

@@ -130,9 +130,8 @@ in mkIf (config.flavor == "lineageos")
   envVars.RELEASE_TYPE = mkDefault "EXPERIMENTAL";  # Other options are RELEASE NIGHTLY SNAPSHOT EXPERIMENTAL
 
   # LineageOS flattens all APEX packages: https://review.lineageos.org/c/LineageOS/android_vendor_lineage/+/270212
-  # I can't find the CI config where this env var is set, but all device ROMS I
-  # tried had flattened APEX packages as of 2020-07-22
   signing.apex.enable = false;
+  # This environment variable is set in android/build.sh under https://github.com/lineageos-infra/build-config
   envVars.OVERRIDE_TARGET_FLATTEN_APEX = "true";
 
   # LineageOS needs this additional command line argument to enable