[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.
7 jobs for pr/241 in 10 minutes and 28 seconds (queued for 1 second)
Status Name Job ID Coverage
  Test
passed doc-coverage #124305

00:09:30

75.0%
failed format #124306
allowed to fail

00:00:26

passed robotpkg-py-eigenpy-18.04 #124300

00:08:15

passed robotpkg-py-eigenpy-20.04 #124301

00:09:11

passed robotpkg-py-eigenpy-buster #124302

00:07:10

passed robotpkg-py-eigenpy-ferrum #124303

00:05:45

passed robotpkg-py-eigenpy-stretch #124304

00:10:27

 
Name Stage Failure
failed
format Test
./unittest/python/test_LDLT.py:14:19: W291 trailing whitespace
./unittest/python/test_LDLT.py:15:19: W291 trailing whitespace
./unittest/python/test_LDLT.py:16:27: W291 trailing whitespace
./unittest/python/test_LDLT.py:18:92: E231 missing whitespace after ','
./benchmarks/bench-switch.py:6:1: F401 'time' imported but unused
./benchmarks/bench-switch.py:7:1: F401 'timeit' imported but unused
./benchmarks/bench-switch.py:53:24: E703 statement ends with a semicolon
Cleaning up file based variables
ERROR: Job failed: exit code 1