Package downloads: allow restricting to primary site only

@@ -119,6 +119,16 @@ config BR2_PRIMARY_SITE
 	  NOTE: This works for all packages using the central package
 	  infrastructure (generic, autotools, cmake, ...)
 
+config BR2_PRIMARY_SITE_ONLY
+	bool "Only allow downloads from primary download site"
+	help
+	  If this option is enabled, downloads will only be attempted from the
+	  primary download site. Other locations, like the package's official
+	  download location or the backup download site, will not be
+	  considered.
+
+if !BR2_PRIMARY_SITE_ONLY
+
 config BR2_BACKUP_SITE
 	string "Backup download site"
 	default "http://sources.buildroot.net/"

@@ -175,6 +185,8 @@ config BR2_DEBIAN_MIRROR
 	  Usually, just add your country code like XX here:
 	  http://ftp.XX.debian.org
 
+endif
+
 endmenu
 
 config BR2_JLEVEL

@@ -189,8 +189,8 @@ endef
 ################################################################################
 # DOWNLOAD -- Download helper. Will try to download source from:
 # 1) BR2_PRIMARY_SITE if enabled
-# 2) Download site
-# 3) BR2_BACKUP_SITE if enabled
+# 2) Download site, unless BR2_PRIMARY_SITE_ONLY is set
+# 3) BR2_BACKUP_SITE if enabled, unless BR2_PRIMARY_SITE_ONLY is set
 #
 # Argument 1 is the source location
 # Argument 2 is the source filename

@@ -210,6 +210,9 @@ define DOWNLOAD_INNER
 			*) $(call $(DL_MODE)_WGET,$(BR2_PRIMARY_SITE)/$(2),$(2)) && exit ;; \
 		esac ; \
 	fi ; \
+	if test "$(BR2_PRIMARY_SITE_ONLY)" = "y" ; then \
+		exit 1 ; \
+	fi ; \
 	if test -n "$(1)" ; then \
 		case "$($(PKG)_SITE_METHOD)" in \
 			git) $($(DL_MODE)_GIT) && exit ;; \