fake:

package/base/alsa-driver/alsa-driver.conf

@@ -32,5 +32,5 @@ var_append confopt ' ' "--with-kernel=$root/usr/src/linux"
 
 # otherwise alsa installs other crap like an init scrpit ...
 makeinstopt="$makeopt install-modules install-headers"
-postmake="$postmake cp -r utils/alsasound snddevices $docdir"
+postmake="$postmake cp -r utils/alsasound snddevices $docdir && rm -f $root/usr/src/linux/.tmp_gas_check"