bootchartd: depends on tar -z functionality

[Thomas De Schampheleire]

Hi,

The bootchartd applet writes its results with 'tar -z' which only
works if the system has a full 'tar' and 'gzip', or has busybox tar
but with gzip functionality enabled (FEATURE_SEAMLESS_GZ).

Currently there is no check on this whatsoever, and bootchartd simply
fails to write its data on the filesystem.

What is the best approach here?

1. let bootchartd depend on FEATURE_SEAMLESS_GZ: trivial change, but
hides bootchartd from config if this feature is not enabled; can be
confusing. Also, if the user has a real non-busybox tar that supports
'-z' this is not needed.

2. let bootchartd select FEATURE_SEAMLESS_GZ: trivial change, but
makes busybox include features the user is not really aware of. Also
not needed in case there is a full 'tar -z'.

3. change bootchartd to write uncompressed data

4. change bootchartd to check if compression is possible. If yes, do
it, if not then write as plain tar.

5. other options?

Thanks,
Thomas