configure, fix for newer gcc

diff --git a/configure b/configure
index 786d249..5bb6fcb 100755 (executable)
--- a/configure
+++ b/configure
@@ -31,7 +31,7 @@ check_option()
 
 check_define()
 {
-  $CC -E -dD $CFLAGS pico/arm_features.h | grep -q $1 || return 1
+  $CC -E -dD $CFLAGS pico/arm_features.h | grep -q "define[    ]*$1" || return 1
   return 0
 }