bitbake: siggen: Print warning about tainted tasks

The big warning printed when people use -f is easily ignored/forgotten.
To raise user awareness, print a warning any time we include a tainted
stamp file into a build instead.

(Bitbake rev: 18f9bcbad059608e22fca20309314e1c399acec7)

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

bitbake/lib/bb/siggen.py

@@ -190,6 +190,7 @@ class SignatureGeneratorBasic(SignatureGenerator):
         taint = self.read_taint(fn, task, dataCache.stamp[fn])
         if taint:
             data = data + taint
+            logger.warn("%s is tainted from a forced run" % k)
 
         h = hashlib.md5(data).hexdigest()
         self.taskhash[k] = h