Move orig_cflags="$CFLAGS" to after AC_PROG_CC_C99

As otherwise the shipped libs don't (necessarily) get -O2 -g,
which in turn means _FORTIFY_SOURCE=3 won't work.

configure

@@ -2698,7 +2698,6 @@ if test "x$enable_dynamic_linking" = "x"; then
 	exit 1
 fi
 
-orig_cflags="$CFLAGS"
 
 BUILDDIR_NOW="`pwd`"
 
@@ -4096,6 +4095,8 @@ then :
   as_fn_error $? "No C99 compiler was found. Please install gcc or clang and other build tools. Eg, on Debian/Ubuntu you probably want to run the following as root: apt-get install build-essential " "$LINENO" 5
 fi
 
+orig_cflags="$CFLAGS"
+
 # Extract the first word of "gmake", so it can be a program name with args.
 set dummy gmake; ac_word=$2
 { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5