base.bbclass: Ensure an empty do_build tasks exists to silence a warning

The message "WARNING: Function do_build doesn't exist" doesn't look professional,
so fix the underlying problem even if this warning is harmless.

Signed-off-by: Richard Purdie <rpurdie@linux.intel.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/meta/classes/base.bbclass b/meta/classes/base.bbclass
index 1547ed0305..f540b58fbb 100644
--- a/meta/classes/base.bbclass
+++ b/meta/classes/base.bbclass
@@ -438,6 +438,9 @@ base_do_package() {
 addtask build after do_populate_sysroot
 do_build = ""
 do_build[func] = "1"
+do_build () {
+        :
+}
 
 python () {
     import exceptions, string