Configure: fixed autotest cleanup commands.

Previously, if configured with --with-cc="clang -g", the autotest.dSYM
directories were left unremoved.

auto/cc/sunc

diff --git a/auto/cc/sunc b/auto/cc/sunc
index dd9cced..8f12d7c 100644
--- a/auto/cc/sunc
+++ b/auto/cc/sunc
@@ -30,7 +30,7 @@
     ngx_sunc_ver=`$NGX_AUTOTEST`
 fi
 
-rm $NGX_AUTOTEST*
+rm -rf $NGX_AUTOTEST*
 
 # 1424 == 0x590, Sun Studio 12