[source] build: ensure that prereq-build is run before metadata scan from feeds (FS#367)

[LEDE Commits]

nbd pushed a commit to source.git, branch master:
https://git.lede-project.org/d2ddda691eeac92c6854658fb7389b7f9485d6c8

commit d2ddda691eeac92c6854658fb7389b7f9485d6c8
Author: Felix Fietkau <nbd at nbd.name>
AuthorDate: Thu Jan 5 11:49:58 2017 +0100

    build: ensure that prereq-build is run before metadata scan from feeds (FS#367)
    
    Fixes ./scripts/feeds update
    
    Signed-off-by: Felix Fietkau <nbd at nbd.name>
---
 include/toplevel.mk | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/toplevel.mk b/include/toplevel.mk
index 5e99df8..24e4ebf 100644
--- a/include/toplevel.mk
+++ b/include/toplevel.mk
@@ -67,7 +67,7 @@ SUBMAKE:=umask 022; $(SUBMAKE)
 
 ULIMIT_FIX=_limit=`ulimit -n`; [ "$$_limit" = "unlimited" -o "$$_limit" -ge 1024 ] || ulimit -n 1024;
 
-prepare-mk: FORCE ;
+prepare-mk: staging_dir/host/.prereq-build FORCE ;
 
 ifdef SDK
   IGNORE_PACKAGES = linux