cm_cxx_features: Filter out MSBXXXX warnings
After this MR, when test compiling a c++ source during cmake compilation, warnings containing MSB[0-9][0-9][0-9][0-9]
will be ignored.
This happened when cmake is built in a subdirectory of the system temporary directory (cwd subdirectory of %TMP%)
It has been tested on previous releases of cmake at https://github.com/conan-io/conan-center-index/pull/3109
Fixes: #21270 (closed)
Edited by Brad King