cmake: Log warnings in CMakeLists.txt
cmake: Log warnings in CMakeLists.txt

Previously, warnings genereated in CMake were not logged because
CMake sends them to stderr alongside the trace information. With
this PR, only real trace lines are send to the trace parser and
all other lines in stderr are logged as warnings.

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