devtool: fix devtool upgrade with reproducible_builds class
If the reproducible_build class is inherited then there may be a
"source-date-epoch" subdirectory in a fetched source tree; devtool
upgrade was not expecting that in the upgraded source. Take a small
snippet of code from recipetool create which already handles this,
and make it a shared function that can be used in both places.
Additionally, fix an assumption that the source is always in a
subdirectory in the cleanup code that blocked debugging this.
[YOCTO #13635]
Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
