OK. I've got something more to report now.
Recently the FreshPaint app in Windows Store was updated to version 2.0.14057.1, and I got a copy of the ARM version of this app, here is what I found inside it.
FreshPaint.exe/FreshPaint.dll have a resource with type "PNBUILDINFO", it is actually a text data:
Build Type: ret
ilc.exe : 1.0.21406.00 built by: PROJECTNREL
Microsoft.Build.ILTasks.dll : 1.0.21406.00 built by: PROJECTNREL
nutc_driver.exe : 1.0.21406.00 built by: PROJECTNREL
rhbind.exe : 1.0.21406.0 (ProjectNRel(DDBLD050B-dlab).021406-0000)
sg.exe : 1.0.21406.00 built by: PROJECTNREL
corefx.dll : 1.0.21406.00 built by: PROJECTNREL
there are some stuff I have speculated before, like ilc.exe, rhbind.exe and corefx.dll.
also note the version string is PROJECTNREL, "REL" usually means its in the RTM branch, and may be released soon.
it also shipps a new version of mrt100_app.dll version is "1.0.30319.18186 (ProjectNRel(DDBLD869A-dlab).021406-0000)", and clrcompression.dll version "1.0.21406.00 built by: PROJECTNREL"
I guess we will finally see this stuff VERY SOON :D