minidump-2-core: Allow user to override shared lib basedir.

minidump-2-core: Allow user to override shared lib basedir.

This CL introduces "--sobasedir" command-line option to minidump-2-core.
By default, paths to shared lib files included in generated core file are
formatted as "/var/lib/breakpad/[GUID]libFoobar.so". By using "--sobasedir",
this will be "[user-supplied-path]libFoobar.so".

This option can be used to ease debugging minidump files from developer's local
builds. By specifying "minidump-2-core --sobasedir `pwd`/out/Debug/lib/
foobar.mdmp", user can load the generated core file in gdb without setting up
the symlinks for "/var/lib/breakpad".

BUG=None
A=kouhei@chromium.org

Original code review: https://breakpad.appspot.com/1214002/

R=kouhei@chromium.org

Committed: https://code.google.com/p/google-breakpad/source/detail?r=1317

[kouhei]

lgtm

[Lei Zhang (chromium)]

Committed patchset #1 manually as r1317 (presubmit successful).