tools: fakeroot: rework relocatable patch to avoid LD_LIBRARY_PATH usage

tools: fakeroot: rework relocatable patch to avoid LD_LIBRARY_PATH usage

Due to the use of LD_LIBRARY_PATH, the programs running in the fakeroot
environment may end up loading bundled SDK libraries using the system
ld.so.

Rework the relocatability patch to avoid meddling with LD_LIBRARY_PATH
and construct the paths to faked and libfakeroot.so directly.

Fixes: f93cb5c2c8 ("fakeroot: make fakeroot script relocatable")
Reviewed-by: Petr Štetiar <ynezz@true.cz>
Signed-off-by: Jo-Philipp Wich <jo@mein.io>