Fix GetExecutablePath on Linux
Fix GetExecutablePath on Linux

It was using lstat to get the size of /proc/self/exe but
it always returns 0, so we just use a big buffer on the
stack instead.

BUG=angleproject:892

Change-Id: I6d88efeb4ec5de7a78cb3668e3d78520203ad1d5
Reviewed-on: https://chromium-review.googlesource.com/269990
Reviewed-by: Kenneth Russell <1ebccd90c2bc76de65b6f830f2128a91ed69fdfb@chromium.org>
Reviewed-by: Jamie Madill <7e492b4f1c8458024932de3ba475cbf015424c30@chromium.org>
Tested-by: Corentin Wallez <470c533e86f4f848c98c7e11fffc2d043494a401@chromium.org>

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