mac: Try harder to get telemetry_perf_unittests/stacktrace_unittest work in component builds.

The test tries to symbolize Chromium Framework independently, so the outer executable's
rpath isn't on the stack. The Framework does have an rpath in component builds, but
it is currently os.path.join(5 * ['..']), which relative to
out/Release/Chromium.app/Contents/Versions/69.0.3456.0/Chromium Framework.framework/Versions/A
gets us to out/Release/Chromium.app/Contents.  That doesn't seem useful for anything
(from what I can tell, it's always been this way since at least the gn switch),
so use 7 * ['..'] instead to get to the build dir.

This possibly fixes a regression from the ancient https://codereview.chromium.org/2700013002

Bug: 850055
Change-Id: I9e65a7fa76620539b2492fd6096b70533a523a74
Reviewed-on: https://chromium-review.googlesource.com/1101064
Commit-Queue: Nico Weber <thakis@chromium.org>
Reviewed-by: Robert Sesek <rsesek@chromium.org>
Cr-Commit-Position: refs/heads/master@{#567288}

• chrome/BUILD.gn[diff]