gh-128042: configure complains when CFLAGS=-O0 and --enable-optimizations are set

Author: taegyunkim

configure

@@ -1823,6 +1823,12 @@ fi],
 [AC_MSG_RESULT([no])])
 
 if test "$Py_OPT" = 'true' ; then
+  # Check for conflicting CFLAGS=-O0 and --enable-optimizations
+  case "$CFLAGS" in
+    *-O0*)
+      AC_MSG_ERROR([CFLAGS contains -O0 which conflicts with --enable-optimizations. Please remove -O0 from CFLAGS or do not use --enable-optimizations.])
+      ;;
+  esac
   # Intentionally not forcing Py_LTO='true' here.  Too many toolchains do not
   # compile working code using it and both test_distutils and test_gdb are
   # broken when you do manage to get a toolchain that works with it.  People