Why is LDC built with old version of LDC

[Dennis Cote]

I'm just curious if there is a good reason why LDC is built with 
an old version of LDC? LDC reports the following using the 
--version option

  Jul 20 13:23:42 on ttys000
Denniss-iMac:~ dennis$ ldc2 --version
LDC - the LLVM D compiler (1.16.0):
   based on DMD v2.086.1 and LLVM 8.0.0
   built with LDC - the LLVM D compiler (1.12.0)
   Default target: x86_64-apple-darwin18.6.0
   Host CPU: skylake
   http://dlang.org - http://wiki.dlang.org/LDC

Why is version 1.16.0 built using version 1.12.0? Could the build 
tools not bootstrap the compiler using 1.12.0, and then recompile 
the source for version 1.16.0 using the version 1.16.0 compiler 
built using the older compiler?