Make const ptr assign as function call in clang

- This can act as memory barrier in clang to avoid
  read before assign of a const ptr

Signed-off-by: LoveSy <shana@zju.edu.cn>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/libbb/appletlib.c b/libbb/appletlib.c
index bf26c99..e8c3084 100644
--- a/libbb/appletlib.c
+++ b/libbb/appletlib.c
@@ -247,7 +247,7 @@
 		IF_FEATURE_INDIVIDUAL(, char **argv))
 {
 #ifdef bb_cached_errno_ptr
-	ASSIGN_CONST_PTR(bb_errno, get_perrno());
+	ASSIGN_CONST_PTR(&bb_errno, get_perrno());
 #endif
 	applet_name = applet;