sstate: Ensure sstate searches update file mtime

Commands like "bitbake XXX -S printdiff" search for sstate files but don't download
them. This means that local files aren't touched as the download code would do, meaning
the sstate cleanup scripts can delete them. This can then lead to obtuse build failures.

Have the search code touch local files in the same way as the main code paths would to
avoid these files disappearing.

Move the function to a common touch() function in lib/oe instead of duplicating code.

(From OE-Core rev: 427c43d8e3315fa6872feaa71d135de60c810de7)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit a27fc0bd5706ab5b9c68a0271fcf57377a678cdf)
Signed-off-by: Steve Sakoman <steve@sakoman.com>

meta/classes-global/sstate.bbclass

@@ -937,6 +937,7 @@ def sstate_checkhashes(sq_data, d, siginfo=False, currentcount=0, summary=True,
         sstatefile = d.expand("${SSTATE_DIR}/" + getsstatefile(tid, siginfo, d))
 
         if os.path.exists(sstatefile):
+            oe.utils.touch(sstatefile)
             found.add(tid)
             bb.debug(2, "SState: Found valid sstate file %s" % sstatefile)
         else:
@@ -1183,16 +1184,7 @@ python sstate_eventhandler() {
         if not os.path.exists(siginfo):
             bb.siggen.dump_this_task(siginfo, d)
         else:
-            try:
-                os.utime(siginfo, None)
-            except PermissionError:
-                pass
-            except OSError as e:
-                # Handle read-only file systems gracefully
-                import errno
-                if e.errno != errno.EROFS:
-                    raise e
-
+            oe.utils.touch(siginfo)
 }
 
 SSTATE_PRUNE_OBSOLETEWORKDIR ?= "1"

meta/lib/oe/utils.py

@@ -7,6 +7,7 @@
 import subprocess
 import multiprocessing
 import traceback
+import errno
 
 def read_file(filename):
     try:
@@ -528,3 +529,14 @@ def directory_size(root, blocksize=4096):
         total += sum(roundup(getsize(os.path.join(root, name))) for name in files)
         total += roundup(getsize(root))
     return total
+
+# Update the mtime of a file, skip if permission/read-only issues
+def touch(filename):
+    try:
+        os.utime(filename, None)
+    except PermissionError:
+        pass
+    except OSError as e:
+        # Handle read-only file systems gracefully
+        if e.errno != errno.EROFS:
+            raise e