[source] build: reset ALTERNATIVES field in Package/Default

[LEDE Commits]

yousong pushed a commit to source.git, branch master:
https://git.lede-project.org/7842ccecc053d1e3b4977334411bb276ace8ae17

commit 7842ccecc053d1e3b4977334411bb276ace8ae17
Author: Yousong Zhou <yszhou4tech at gmail.com>
AuthorDate: Wed May 3 17:30:08 2017 +0800

    build: reset ALTERNATIVES field in Package/Default
    
    Otherwise ipkg packages may wrongly take on alternatives specs of
    another package sharing the same package Makefile
    
    Fixes FS#753
    
    Signed-off-by: Yousong Zhou <yszhou4tech at gmail.com>
---
 include/package-defaults.mk | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/package-defaults.mk b/include/package-defaults.mk
index 6672b67..0eecd6c 100644
--- a/include/package-defaults.mk
+++ b/include/package-defaults.mk
@@ -56,6 +56,7 @@ define Package/Default
   VARIANT:=
   DEFAULT_VARIANT:=
   USERID:=
+  ALTERNATIVES:=
 endef
 
 Build/Patch:=$(Build/Patch/Default)