Memory scripts: Accept --build-dir in addition to --build_dir.

Many more tools accept --build-dir, so try to standardize at that. (Keep
--build_dir around for a while longer so that we can change the bot configs to
the new flag first.)

Most of memory tools use --under_flags, so this increases self-inconsistency a bit, but they already have some --dash-flags (e.g. --help-tests) and the remaining flags are mostly --gtest_filter and friends. Change --source_dir to
--source-dir at least to keep it similar to --build-dir. (And remove --source_dir from tsan_analyze.py, where it was unused.)

BUG=294387
R=scottmg@chromium.org
TBR=thestig

Review URL: https://codereview.chromium.org/25815003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@226623 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 226623