perf_env__set_cmdline() only saves the arguments the first time it's
called.  It doesn't need to be called every time the options and
suboptions are parsed.  Instead it can just be called once.

This also has the advantage of making the option parsing code less
perf-specific so it can be moved out to a library.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/19b76a5aa1b688bd635bd65d80bbc103a978d75e.1449548395.git.jpoimboe@redhat.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>