The Source: variable is generated from FILE but this is excluded from checksums
normally which results in a reproduciubility issue when the filename changes.
Add in a dependency by reworking the code a little to avoid this.
(From OE-Core rev: 3ea7da76c6930031a0071069027b1d71f737fbc9)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>