Setting void CFLAGS and CXXFLAGS if not defined by user
Setting void CFLAGS and CXXFLAGS if not defined by user

Co-authored-by: pantogon <b54d85a0e9429d4bf7c346bf0fac501f03c00911@users.noreply.github.com>

bsc-performance-tools/wxparaver,bsc-performance-tools/wxparaver