sanitycheck failures for native_posix

[andrewboie]

Describe the bug

Keeping artifacts untouched
INFO    - JOBS: 48
INFO    - 3715 tests passed already, retrying 19 tests
INFO    - 19 test configurations selected, 0 configurations discarded due to filters.
INFO    - Adding tasks to the queue...
ERROR   - Cmake build failure: /home/apboie/projects/zephyr/zephyr/samples/drivers/display for native_posix_64

ERROR   - native_posix_64           samples/drivers/display/sample.display.sdl         FAILED: Cmake build failure
ERROR   - see: /dev/shm/sanity-out/native_posix_64/samples/drivers/display/sample.display.sdl/build.log
INFO    - Total complete:    1/  19   5%  skipped:    0, failed:    1
ERROR   - native_posix              tests/application_development/cpp/application_development.cpp.main FAILED: Build failure
ERROR   - see: /dev/shm/sanity-out/native_posix/tests/application_development/cpp/application_development.cpp.main/build.log
INFO    - Total complete:    2/  19  10%  skipped:    0, failed:    2
ERROR   - native_posix              tests/application_development/libcxx/application_development.cpp.libcxx FAILED: Build failure
ERROR   - see: /dev/shm/sanity-out/native_posix/tests/application_development/libcxx/application_development.cpp.libcxx/build.log
INFO    - Total complete:    3/  19  15%  skipped:    0, failed:    3
ERROR   - native_posix              tests/application_development/libcxx/application_development.cpp.libcxx.exceptions FAILED: Build failure
ERROR   - see: /dev/shm/sanity-out/native_posix/tests/application_development/libcxx/application_development.cpp.libcxx.exceptions/build.log
INFO    - Total complete:    4/  19  21%  skipped:    0, failed:    4

From logs this was CMAKE complaining about no SDL libraries, and a missing bits/c++config.h

I fixed it on my Ubuntu machine with

$ sudo apt install g++-multilib libsdl2-dev

I don't know what the package names are on other distros.
We need to update the getting started directions.