Remove hardcoded CFLAGS.

Index: configure
--- configure.orig
+++ configure
@@ -20238,7 +20238,7 @@ else $as_nop
 printf "%s\n" "yes" >&6; }
 fi
 
-AM_CFLAGS="$AM_CFLAGS -g -O3"
+AM_CFLAGS="$AM_CFLAGS -g"
 if test x"$GCC" = "xyes"; then
     AM_CFLAGS="$AM_CFLAGS -ffast-math"
 fi
