configure: fix check_cmd in check_host_cpp

Use correct cpp and c flags variables for the host libc.
Signed-off-by: Jörg Krause <jkrause@posteo.de>
Reviewed-by: Benoit Fouet <benoit.fouet@free.fr>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

configure

@@ -1244,7 +1244,7 @@ check_host_cpp(){
     log check_host_cpp "$@"
     cat > $TMPC
     log_file $TMPC
-    check_cmd $host_cc $HOSTCPPFLAGS $HOSTCFLAGS "$@" $(hostcc_e $TMPO) $TMPC
+    check_cmd $host_cc $host_cppflags $host_cflags "$@" $(hostcc_e $TMPO) $TMPC
 }
 
 check_host_cppflags(){