package/qt5base: disable feature-relocatable

Disable feature-relocatable to avoid a path mismatch while searching qml
files and buildroot BR2_ROOTFS_MERGED_USR feature enabled.

As described in [1] with feature-relocatable Qt determines the search
pathes relative to the location of libQt5Core.so, with BR2_ROOTFS_MERGED_USR
enabled found first under the symlink path '/lib' instead of the install
path '/usr/lib' and searches sequentially for qml files under '/qml' instead
of the correct '/usr/qml'.

Fixes:
  - https://bugs.busybox.net/show_bug.cgi?id=12906

[1] https://code.qt.io/cgit/qt/qtbase.git/commit/?id=4ac872639ed0dd3ae6627e05bdda821f7d128500



Reported-by: Joonas Harjumäki <jharjuma@gmail.com>
Signed-off-by: Peter Seiderer <ps.report@gmx.net>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>