[OE-core] [PATCH] bitbake.conf: Set PACKAGE_ARCH with ??=

[Richard Purdie]

Currently its near impossible for other classes to sanely override
this value with their own default. By setting a weak default we can 
allow other classes to change the default and allow end recipes to
again override this.

As far as I can tell, there shouldn't be any regressions from this
change.

Signed-off-by: Richard Purdie <richard.purdie at linuxfoundation.org>

diff --git a/meta/conf/bitbake.conf b/meta/conf/bitbake.conf
index ef30cb6..2537ef1 100644
--- a/meta/conf/bitbake.conf
+++ b/meta/conf/bitbake.conf
@@ -133,7 +133,7 @@ SDK_LD_ARCH = "${BUILD_LD_ARCH}"
 SDK_AS_ARCH = "${BUILD_AS_ARCH}"
 
 TUNE_PKGARCH ??= ""
-PACKAGE_ARCH = "${TUNE_PKGARCH}"
+PACKAGE_ARCH ??= "${TUNE_PKGARCH}"
 MACHINE_ARCH = "${@[d.getVar('TUNE_PKGARCH', True), d.getVar('MACHINE', True)][bool(d.getVar('MACHINE', True))].replace('-', '_')}"
 PACKAGE_EXTRA_ARCHS ??= "${PACKAGE_EXTRA_ARCHS_tune-${DEFAULTTUNE}}"
 PACKAGE_ARCHS = "all any noarch ${PACKAGE_EXTRA_ARCHS} ${MACHINE_ARCH}"