runqemu: time the copy to tmpfs

Measure and display the time it takes to copy the rootfs to its new
location (usually in tmpfs) to try to understand whether it sometimes takes
a lot of time on the autobuilders.

(From OE-Core rev: be213114c1349e02ca48fd617a6c3badae8aa101)

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/runqemu

@@ -18,6 +18,7 @@ import shutil
 import glob
 import configparser
 import signal
+import time
 
 class RunQemuError(Exception):
     """Custom exception to raise on known errors."""
@@ -1201,8 +1202,10 @@ class BaseConfig(object):
         tmpfsdir = os.environ.get("RUNQEMU_TMPFS_DIR", None)
         if self.snapshot and tmpfsdir:
             newrootfs = os.path.join(tmpfsdir, os.path.basename(self.rootfs)) + "." + str(os.getpid())
+            logger.info("Copying rootfs to %s" % newrootfs)
+            copy_start = time.time()
             shutil.copyfile(self.rootfs, newrootfs)
-            #print("Copying rootfs to tmpfs: %s" % newrootfs)
+            logger.info("Copy done in %s seconds" % (time.time() - copy_start))
             self.rootfs = newrootfs
             # Don't need a second copy now!
             self.snapshot = False