Configure: removed redundant auto/have call.

The auto/feature call above is enough to set NGX_HAVE_SENDFILE.

auto/os/darwin

diff --git a/auto/os/darwin b/auto/os/darwin
index b97518a..1d3e3d3 100644
--- a/auto/os/darwin
+++ b/auto/os/darwin
@@ -100,7 +100,6 @@
 . auto/feature
 
 if [ $ngx_found = yes ]; then
-    have=NGX_HAVE_SENDFILE . auto/have
     CORE_SRCS="$CORE_SRCS $DARWIN_SENDFILE_SRCS"
 fi