dnl Default to empty (i.e. assigning the null string to) CFLAGS and CXXFLAGS,
dnl instead of the autoconf default (for example, '-g -O2' for CC=gcc).
dnl Default to empty (i.e. assigning the null string to) CFLAGS and CXXFLAGS,
dnl instead of the autoconf default (for example, '-g -O2' for CC=gcc).