Use MacPorts CXXFLAGS.
--- configure.ac.orig	2023-08-10 15:49:35.000000000 -0500
+++ configure.ac	2023-08-10 22:35:12.000000000 -0500
@@ -124,8 +124,6 @@
 # For -I and -D flags
 CPPFLAGS="$CPPFLAGS $cppflag"
 
-# For debugging and optimization ... overwrite default because it has both -g and -O2
-CXXFLAGS="$cxxflag"
 
 # Check compiler and use -Wall if gnu.
 if [test $GXX = "yes" ;] then