Granulate perf v5.12 (v1)

perf inject: Keep previous cmdline

Force "perf inject" to write the cmdline it has read from the input file,
instead of writing its own cmdline. "perf inject" cmdline is hardly useful,
"perf record"s is what we care about.

Do note it's not exactly complete - I did not change write_cmdline() so
that one still writes readlink("/proc/self/exe") of "perf inject" as the
argv[0], and we drop the argv[0] we've read from the file. Unless you use
different "perf" binaries for "record" and "inject", this doesn't matter.

Signed-off-by: Yonatan Goldschmidt <yonatan.goldschmidt@granulate.io>