bitbake: bitbake: reset build mtime cache before the build

Introduced build mtime cache structure. Reset it before the build
to prevent bitbake from crashing when build/tmp/stamps hierarchy
is removed.

[YOCTO: #7562]

(Bitbake rev: f8590547a198a78334debdf14bf40acb50c22ecc)

Signed-off-by: Ed Bartosh <ed.bartosh@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/build.py

@@ -31,6 +31,7 @@ import logging
 import shlex
 import glob
 import time
+import stat
 import bb
 import bb.msg
 import bb.process
@@ -42,6 +43,20 @@ logger = logging.getLogger('BitBake.Build')
 
 NULL = open(os.devnull, 'r+')
 
+__mtime_cache = {}
+
+def cached_mtime_noerror(f):
+    if f not in __mtime_cache:
+        try:
+            __mtime_cache[f] = os.stat(f)[stat.ST_MTIME]
+        except OSError:
+            return 0
+    return __mtime_cache[f]
+
+def reset_cache():
+    global __mtime_cache
+    __mtime_cache = {}
+
 # When we execute a Python function, we'd like certain things
 # in all namespaces, hence we add them to __builtins__.
 # If we do not do this and use the exec globals, they will
@@ -535,7 +550,7 @@ def stamp_internal(taskname, d, file_name, baseonly=False):
     stamp = bb.parse.siggen.stampfile(stamp, file_name, taskname, extrainfo)
 
     stampdir = os.path.dirname(stamp)
-    if bb.parse.cached_mtime_noerror(stampdir) == 0:
+    if cached_mtime_noerror(stampdir) == 0:
         bb.utils.mkdirhier(stampdir)
 
     return stamp