Allow C++ exceptions on cros-disks.

cros-disks uses try/catch to interact with dbus-c++.

BUG=chromium:386443
TEST=emerge-link platform2 (with the changes to common.gypi)
CQ-DEPEND=CL:205242

Change-Id: Ib2f34fe23d2806bc4b8d6344c65de9bac5165498
Reviewed-on: https://chromium-review.googlesource.com/205228
Reviewed-by: Ben Chan <benchan@chromium.org>
Commit-Queue: Alex Deymo <deymo@chromium.org>
Tested-by: Alex Deymo <deymo@chromium.org>
diff --git a/cros-disks.gyp b/cros-disks.gyp
index 9e38b55..18e7abb 100644
--- a/cros-disks.gyp
+++ b/cros-disks.gyp
@@ -18,6 +18,8 @@
         'libchromeos-<(libbase_ver)',
         'libudev',
       ],
+      # cros-disks uses try/catch to interact with dbus-c++.
+      'enable_exceptions': 1,
     },
     'cflags_cc': [
       '-std=gnu++11',