bitbake: build.py: check dependendent task for addtask

The following command is incorrect, but was ignored silently, that may suprise
users:

addtask task after task_not_existed

This patch can check and warn for it. It would be better to also check "before"
tasks, but there is no easier way to do it.

[YOCTO #13282]

(Bitbake rev: b1ad36169c2ad189d84c53c707b66c12d5ff812f)

Signed-off-by: Robert Yang <liezhi.yang@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/build.py

@@ -815,6 +815,9 @@ def add_tasks(tasklist, d):
         task_deps['parents'][task] = []
         if 'deps' in flags:
             for dep in flags['deps']:
+                # Check and warn for "addtask task after foo" while foo does not exist
+                if not dep in tasklist:
+                    bb.warn('%s: dependent task %s does not exist' % (d.getVar('PN'), dep))
                 dep = d.expand(dep)
                 task_deps['parents'][task].append(dep)