Fix running actions and rules on make/mac

Fix running actions and rules on make/mac

Libraries for the target toolset are in a different location on mac, and
we need to use DYLD_LIBRARY_PATH instead of LD_LIBRARY_PATH.

BUG=none

[jochen (gone - plz use gerrit), 2013-08-06 09:38:10]

r?

any idea how to test?

[jochen (gone - plz use gerrit), 2013-08-07 05:55:19]

Mark, can you have a look please?

[Mark Mentovai, 2013-08-07 13:25:17]

I don’t think we set DYLD_LIBRARY_PATH for Mac builds under ninja or xcodebuild.
But all of that works differently on the Mac than other platforms anyway:
executables refer to libraries by path, which can be absolute, so for things in
the built products directory as well as anywhere else on the system, they can
just say “the library is in the same directory that I’m in” and this doesn’t
become a problem.

This doesn’t seem too hard to test. I guess you’d want to do target_with_action
-> executable -> shared_library (-> is a dependency relationship), and you’d
want to verify that the action in target_with_action ran by checking for some
visible-in-the-filesystem change performed by code baked into shared_library.

[jochen (gone - plz use gerrit), 2013-08-14 13:03:40]

this only works on windows, and linux (make)

for all other configurations it fails :-/

I guess I just give up and note this down under "not supported".