local.conf.sample: use ?= to assign BB_ENV_EXTRAWHITE variables

Use ?= so that the BB_ENV_EXTRAWHITE variables can be overridden from
the environment.

[YOCTO #4367]

Signed-off-by: Jesse Zhang <sen.zhang@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

diff --git a/meta-yocto/conf/site.conf.sample b/meta-yocto/conf/site.conf.sample
index b2d01d0c5902c92d43d520c7306a4a69115f0b45..c551e8fb0c478d4cfe85fbd62553540b96ae3754 100644 (file)
--- a/meta-yocto/conf/site.conf.sample
+++ b/meta-yocto/conf/site.conf.sample
@@ -19,10 +19,10 @@ SCONF_VERSION = "1"
 # To use git with a proxy, you must use an external git proxy command, such as
 # the one provided by scripts/oe-git-proxy.sh. To use this script, copy it to
 # your PATH and uncomment the following:
-#GIT_PROXY_COMMAND="oe-git-proxy"
-#ALL_PROXY="socks://socks.example.com:1080"
+#GIT_PROXY_COMMAND ?= "oe-git-proxy"
+#ALL_PROXY ?= "socks://socks.example.com:1080"
 #or
-#ALL_PROXY="https://proxy.example.com:8080"
+#ALL_PROXY ?= "https://proxy.example.com:8080"
 # If you wish to use certain hosts without the proxy, specify them in NO_PROXY.
 # See the script for details on syntax.