UPDATE: We were able to get around this issue by renaming our external drives.
The actual problem is that Mono's xbuild fails to build UnrealBuildTool
QA REGRESSION: Yes
Mac editor fails to compile in Xcode if the path to the build has spaces in it. Syncing a new build seems to be the key. The issue will not occur if you just add a space and generate project files.
User receives the following error:
ERROR: System.ComponentModel.Win32Exception: ApplicationName='/Volumes/Seagate Backup Plus Drive/Main/UE4/Engine/Binaries/DotNET/UnrealBuildTool.exe', CommandLine='UnrealHeaderTool Mac Development -NoMutex', CurrentDirectory='', Native error= Cannot find the specified file
NOTE: There is a similar error when running GenerateProjectFiles.command, though it still successfully creates the project file:
/Volumes/Seagate Backup Plus /Drive/Main/UE4/Engine/Binaries/ThirdParty/Mono/Mac/lib/mono/4.5/ /Microsoft.CSharp.targets: error : Error executing tool /'/Volumes/Seagate Backup Plus /Drive/Main/UE4/Engine/Binaries/ThirdParty/Mono/Mac/lib/mono/4.5/mcs.exe /': ApplicationName='/Volumes/Seagate Backup Plus /Drive/Main/UE4/Engine/Binaries/ThirdParty/Mono/Mac/lib/mono/4.5/mcs.exe /', CommandLine='/noconfig /@/var/folders/kc/_fjvz5vx3cx9y29fr0llf0km0000gr/T/tmp5cc01e76.tmp', /CurrentDirectory='/Volumes/Seagate Backup Plus /Drive/Main/UE4/Engine/Source/Programs/UnrealBuildTool', Native error= /Cannot find the specified file
1. Sync the engine folder back one label.
2. In your build path, add a space. For example, we changed the name of our external drive from "Data" to "Data Test" (but it doesn't have to be an external drive.
3. Fix your Perforce workspace so it matches the new path.
4. Sync your engine folder to a newer label.
5. Once syncing is done, run GenerateProjectFiles.command.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-7164 in the post.