parser: fix build issue with REALLOCARRAY check
On some systems the build of the parser is spitting out
cc: fatal error: no input files
compilation terminated.This is being caused by the REALLOCARRAY checkfailing due to cpp trying to check for both input and output files and not correctly falling back to stdin/stdout if infile and outfile aren't specified.
Fix this by being explicit that infile and outfile are supposed to use stdin and stdout.
Signed-off-by: John Johansen john.johansen@canonical.com