I’m actually having the exact same issue. Every time I attempt to build the engine or personal project it completely rebuilds - even without touching a single file. I am on professional. I’m only going to add a few details here to Angel’s explanation above in hopes something can be done to fix it other than having to change the code above.
I only started getting this AFTER I made a shipping build using the “RunUAT BuildGraph” command. Everything before doing that worked just fine( took seconds to compile changes ). I had all sorts of issues however with getting RunUAT BuildGraph to run. First my computer only had VS 2012 and VS 2017 and it seems it needed to have VS2015 so I installed that. Here is that bug:
Once I got everything building a shipping version, I went back to build the editor in “development editor” and that’s when it broke. I figured I just needed to do a clean. Which I did and still same result. ( again just building without touching anything does a full rebuild )
Figured I did something stupid when attempting to get the runUAT BuildGraph script running. The thing is I only touched the installedEngineBuild.xml. I can’t imagine that has anything to do with building locally. However, I did revert it. Same thing.
In what I thought was surely going to fix it, I blow away my custom unreal engine( from github ) and resynced. Rebuilt. Then did a quick build with no changes and it fully rebuilds. - not fixed.
I decided to remove VS2015 and VS2017 and reinstalled VS2017. Same thing.
I added the verbose to my buildconfiguration.xml as mentioned above. I’ve attached it. Interestingly it now is saying…
12>UnrealBuildTool: VERBOSE: Couldn’t resolve included file “x.h”
There are a ton of header files listed.
I’m going to keep looking and hope for a none code change.