[CMake] set INSTALL_RPATH for python on linux

To avoid the need to set `LD_LIBRARY_PATH` when the
`CMAKE_INSTALL_PREFIX` is not a standard one.
12 jobs for pr/237 in 44 minutes and 16 seconds (queued for 2 seconds)
Name Stage Failure
failed
robotpkg-py-hpp-fcl-buster Test

Total Test time (real) = 47.61 sec

The following tests FAILED:
16 - gjk (Child aborted)
Errors while running CTest
make: *** [Makefile:110: test] Error 8
Cleaning up file based variables
ERROR: Job failed: exit code 1
failed
robotpkg-hpp-fcl-buster Test
Total Test time (real) =  49.31 sec

The following tests FAILED:
16 - gjk (Child aborted)
18 - serialization (Child aborted)
Errors while running CTest
make: *** [Makefile:110: test] Error 8
Cleaning up file based variables
ERROR: Job failed: exit code 1
failed
format Test
./python/hppfcl/viewer.py:77:21: E128 continuation line under-indented for visual indent
./python/hppfcl/viewer.py:77:65: E231 missing whitespace after ','
./python/hppfcl/viewer.py:77:67: E231 missing whitespace after ','
./python/hppfcl/__init__.py:34:1: F403 'from .hppfcl import *' used; unable to detect undefined names
./python/hppfcl/__init__.py:34:1: F401 '.hppfcl.*' imported but unused
./python/hppfcl/__init__.py:35:1: F401 '.hppfcl.__version__' imported but unused
./python/hppfcl/__init__.py:35:1: F401 '.hppfcl.__raw_version__' imported but unused
Cleaning up file based variables
ERROR: Job failed: exit code 1