tests: make chdir more robust in run_unittests.py
tests: make chdir more robust in run_unittests.py

jpakkane/meson,jpakkane/meson,pexip/meson,mesonbuild/meson,jpakkane/meson,QuLogic/meson,jpakkane/meson,mesonbuild/meson,QuLogic/meson,pexip/meson,jpakkane/meson,QuLogic/meson,QuLogic/meson,QuLogic/meson,QuLogic/meson,mesonbuild/meson,pexip/meson,jpakkane/meson,mesonbuild/meson,QuLogic/meson,pexip/meson,mesonbuild/meson,pexip/meson,jpakkane/meson,QuLogic/meson,jpakkane/meson,jpakkane/meson,pexip/meson,mesonbuild/meson,pexip/meson,mesonbuild/meson,mesonbuild/meson,mesonbuild/meson,pexip/meson,pexip/meson,pexip/meson,QuLogic/meson,mesonbuild/meson