Lighting Build Stuck at 0% [OS X]

I built the promoted branch using Xcode 7.3.

When I first tried to build lighting, the lightness app complained about some missing embree libs. I copied them to UnrealEditor.app/Contets/MacOS and the lighting build started. However it is stuck at 0% for hours (no matter what project I use it with). My Firewall is deactivated, so this should not be an issue.

When the build starts, Xcode displays the following message:

Not using cached read wrapper
LogInit:Display: RandInit(2102834749) SRandInit(2102836389).
RandInit(2102834749) SRandInit(2102836389).
Using version manifest at CL 0 with build ID 'a91f025a-f490-446d-8e63-32a152bbd821'
Started task graph with 3 named threads and 6 total threads with 1 sets of task threads.
Version: 4.12.0-0+UE4
API Version: 0
Number of dev versions registered: 13
  Dev-Blueprints (B0D832E4-1F89-4F0D-ACCF-7EB736FD4AA2): 2
  Dev-Build (E1C64328-A22C-4D53-A36C-8E866417BD8C): 0
  Dev-Core (375EC13C-06E4-48FB-B500-84F0262A717E): 0
  Dev-Editor (E4B068ED-F494-42E9-A231-DA0B2E46BB41): 1
  Dev-Framework (CFFC743F-43B0-4480-9391-14DF171D2073): 2
  Dev-Mobile (B02B49B5-BB20-44E9-A304-32B752E40360): 0
  Dev-Networking (A4E4105C-59A1-49B5-A7C5-40C4547EDFEE): 0
  Dev-Online (39C831C9-5AE6-47DC-9A44-9C173E1C8E7C): 0
  Dev-Physics (78F01B33-EBEA-4F98-B9B4-84EACCB95AA2): 0
  Dev-Platform (6631380F-2D4D-43E0-8009-CF276956A95A): 0
  Dev-Rendering (12F88B9F-8875-4AFC-A67C-D90C383ABD29): 0
  Dev-Sequencer (7B5AE74C-D270-4C10-A958-57980B212A5A): 0
  Dev-VR (D7296918-1DD6-4BDD-9DE2-64A83CC13884): 0
Compiled (64-bit): Feb 22 2016 23:59:24
Compiled with Clang: 7.3.0 (clang-703.0.21)
Build Configuration: Development
Branch Name: UE4
Command line: 9ED1E813B24A174A0CB82190358BE5F8 -Messaging
Base directory: /Users/++++/Entwicklung/UnrealEngine/Engine/Binaries/Mac/
Installed Engine Build: 0
Presizing for max 100000 objects, including 0 objects not considered by GC, pre-allocating 0 bytes for permanent pool.
Object subsystem initialized
Computer: MyMac.local
User: ++++
CPU Page size=4096, Cores=4
High frequency timer resolution =1000.000000 MHz
Power Source: AC Power
Memory total: Physical=16.0GB (16GB approx) Pagefile=1.0GB Virtual=17.0GB
No translations for ('de-DE') exist, falling back to 'en' for localization and internationalization data.
LogModuleManager:Warning: ModuleManager: Unable to load module 'Settings' because the file '/Users/++++/Entwicklung/UnrealEngine/Engine/Binaries/Mac/' was not found.
ModuleManager: Unable to load module 'Settings' because the file '/Users/++++/Entwicklung/UnrealEngine/Engine/Binaries/Mac/' was not found.
Initializing bridge on interface 0.0.0.0:0 to multicast group 230.0.0.1:6666.
LogLightmass:Display: Lightmass Mac started on: MyMac.local. Command-line: 9ED1E813B24A174A0CB82190358BE5F8 -Messaging
Lightmass Mac started on: MyMac.local. Command-line: 9ED1E813B24A174A0CB82190358BE5F8 -Messaging
LogLightmass:Display: Processing scene GUID: 9ED1E813B24A174A0CB82190358BE5F8 with 8 threads
Processing scene GUID: 9ED1E813B24A174A0CB82190358BE5F8 with 8 threads
Building static lighting...

Stepping through the Lightness app I found that I get stuck in the first while loop in FSwarmInterfaceLocalImpl::SendMessage, but I don’t now how to proceed from here.

Does anyone have any hint what I could check next to figure out what is going wrong? I am new to UE4, so I basically ran out of ideas…

Thanks.