copy-overlay: document you need to ./build-buildroot afterwards

README.adoc

@@ -11851,13 +11851,15 @@ We use this directory for:
 +
 C files for example need compilation, and must go through the regular package system, e.g. through link:kernel_modules/user[].
 
-This directory is copied into the target filesystem by link:copy-overlay[], which then it visible via <<9p>> on the guest at:
+This directory is copied into the target filesystem by:
 
 ....
-ls /mnt/9p/out_rootfs_overlay
+./copy-overlay
 ....
 
-Furthermore, since this directory does not require compilation, we also make it <<9p>> available to the guest directly even without `copy-overlay` at:
+Source link:copy-overlay[]
+
+Since this directory does not require compilation, we also make it <<9p>> available to the guest directly even without `copy-overlay` at:
 
 ....
 ls /mnt/9p/rootfs_overlay
@@ -11865,6 +11867,19 @@ ls /mnt/9p/rootfs_overlay
 
 This way you can just hack away the scripts and try them out immediately without any further operations.
 
+To add those scripts to the Buildroot root filesystem, you will need to run:
+
+....
+./build-buildroot
+....
+
+We could add that directory to `BR2_ROOTFS_OVERLAY` but we don't do this because this mechanism:
+
+* also works for non Buildroot root filesystesms
+* places everything in one place for a nice 9P mount
+
+and maintaining `BR2_ROOTFS_OVERLAY` in addition to our mechanism would duplicate some logic.
+
 === Test this repo
 
 ==== Automated tests
@@ -11883,7 +11898,7 @@ Sources:
 
 * link:build-test[]
 * link:test[]
-* link:test-module[]
+* link:test-modules[]
 * <<user-mode-tests>>
 * <<baremetal-tests>>