qibuild: fix CMAKE_PREFIX_PATH generation
qibuild: fix CMAKE_PREFIX_PATH generation

Using list(APPEND ...) instead of list(INSERT 0 ...) to
keep the correct order

Change-Id: I9edbb46c27100b1317a3cbb74ab60ff204f05542
Reviewed-on: http://gerrit.aldebaran.lan/55857
Tested-by: gerrit
Reviewed-by: dmerejkowsky <1e4b13000fa8777df4cefd2fd8215187e3deb062@aldebaran-robotics.com>

dmerejkowsky/qibuild,dmerejkowsky/qibuild,aldebaran/qibuild,dmerejkowsky/qibuild,dmerejkowsky/qibuild,aldebaran/qibuild,aldebaran/qibuild,aldebaran/qibuild,dmerejkowsky/qibuild