Introduce mac_want_real_dsym GYP flag. By default, fake .dSYM files

Introduce mac_want_real_dsym GYP flag. By default, fake .dSYM files
will be generated for regular builds, and dsymutils will be used to create .dSYMs for ASan builds.
mac_want_real_dsym can be used to override this.

mac_real_dsym can't be set directly, because it's not a % variable.
According to https://codereview.chromium.org/113999, it can't be made a
% variable now, because of a bug in % handling in GYP that leads to
mac_real_dsym being unconditionally set to 1 for some targets.

BUG=148383
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=173749

[Alexander Potapenko, 2012-12-17 17:30:01]

Please take a look.
I've decided to let the users override the default, because it's usually fine to
use fake dsyms for local ASan builds.
Sorry for keeping this in my queue for too long.

[Nico, 2012-12-18 00:38:25]

The change looks fine, but can you update the CL description to include a bit
more context? (Like why mac_real_dsym can't be set directly – it's not a %
variable, and why that is – link to where Mark added this workaround, etc)

[Alexander Potapenko, 2012-12-18 10:35:39]

Updated the description.
Mark, is there a bug ID for the % issue?

[Mark Mentovai, 2012-12-18 13:33:54]

Not that I recall, but it’s been 3 1/2 years.

[Alexander Potapenko, 2012-12-18 14:36:26]

Nico, please consider pressing the CQ checkbox iff the change looks good now.

[Nico, 2012-12-18 15:56:29]

lgtm

[commit-bot: I haz the power, 2012-12-18 15:56:44]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/glider@chromium.org/11587012/12002

[commit-bot: I haz the power, 2012-12-18 17:50:00]

Change committed as 173749