bb.build: use relative log links, not absolute

Using symlinks to absolute paths isn't gaining us anything, and can cause
problems in situations such as automated build systems when they try to
resolve the link, depending on the mechanism used to pull the build artifacts
(e.g. nfs).

(Bitbake rev: f9cf2671c0ecad153db11bca1aebe151213bfb42)

Signed-off-by: Christopher Larson <chris_larson@mentor.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/build.py

@@ -291,12 +291,13 @@ def _exec_task(fn, task, d, quieterr):
 
     bb.utils.mkdirhier(tempdir)
     loglink = os.path.join(tempdir, 'log.{0}'.format(task))
-    logfn = os.path.join(tempdir, 'log.{0}.{1}'.format(task, os.getpid()))
+    logbase = 'log.{0}.{1}'.format(task, os.getpid())
+    logfn = os.path.join(tempdir, logbase)
     if loglink:
         bb.utils.remove(loglink)
 
         try:
-           os.symlink(logfn, loglink)
+           os.symlink(logbase, loglink)
         except OSError:
            pass