add lsan build

I did try a gcc.lsan build too, but it didn't pass my simple
smoke test of detecting a missing free() in tests.c.  Clang did.

Change-Id: I1d0dce7285e157d4f51952ffc7373cfe54ebee68
Reviewed-on: https://skia-review.googlesource.com/93944
Reviewed-by: Brian Osman <brianosman@google.com>
2 files changed