poky-init-build-env: Update for BASH 4 Bourne Shell semantics

It's no longer valid in bash 4 when invoked with Bourne Shell semantics to
return unless you're inside a sourced script or a function.  Doing so in
this context doesn't actually exit from the setup script.  This should
probably preserve the original intent.

Signed-off-by: Joe MacDonald <joe@deserted.net>
Signed-off-by: Richard Purdie <rpurdie@linux.intel.com>

poky-init-build-env

@@ -22,6 +22,7 @@
 if test x"$0" = x"./poky-init-build-env"; then
    echo "Error: Run via '. ./poky-init-build-env'"
    return
+else
+   . ./scripts/poky-env-internal
 fi
 
-. ./scripts/poky-env-internal