callouts: add argument for output file
callouts: add argument for output file

Some build systems prefer output files being in an out-of-tree
location rather than the pwd.  Add an optional output file
parameter so that the full path to a desired output can be given.

Signed-off-by: Patrick Williams <cbb7353e6d953ef360baf960c122346276c6e320@stwcx.xyz>
Change-Id: Idf412c9b1a651d20907972af49a525707889568c

openbmc/phosphor-logging,openbmc/phosphor-logging,openbmc/phosphor-logging,openbmc/phosphor-logging