Hello,

On the 'core-updates' branch, if you try to reference the 'master'
branch in an inferior, your system will fail to build like so:

Backtrace:
          11 (primitive-load "/gnu/store/m5wq1irm2gb7r4k72qmzf1hi426?")
In ice-9/eval.scm:
    619:8 10 (_ #f)
In srfi/srfi-1.scm:
   466:18  9 (fold #<procedure 7ffff4f17ec0 at ice-9/eval.scm:336:1?> ?)
   466:18  8 (fold #<procedure 7ffff445c500 at ice-9/eval.scm:336:1?> ?)
   466:18  7 (fold #<procedure 7fffeff86ea0 at ice-9/eval.scm:336:1?> ?)
In ice-9/eval.scm:
    619:8  6 (_ #(#(#<directory (guix build utils) 7ffff5c9e500>) # ?))
In ice-9/boot-9.scm:
   2312:4  5 (save-module-excursion _)
In unknown file:
           4 (primitive-load "./guix/build/syscalls.scm")
In ice-9/eval.scm:
    619:8  3 (_ #f)
In ice-9/boot-9.scm:
  2071:24  2 (call-with-deferred-observers #<procedure 7fffeecd2480 ?>)
   260:13  1 (for-each #<procedure 7fffeecd2340 at ice-9/boot-9.scm?> ?)
In unknown file:
           0 (scm-error misc-error #f "~A ~S" ("re-exporting loc?" ?) ?)

ERROR: In procedure scm-error:
re-exporting local variable: AT_SYMLINK_NOFOLLOW
builder for `/gnu/store/3a5d7ykx6wpyw9z1i01w69cafhrzjc21-module-import-compiled.drv' failed with exit code 1
cannot build derivation `/gnu/store/l3kml1yk7ma9d1bybsjvv5iw1khy6b89-compute-guix-derivation.drv': 1 dependencies couldn't be built
guix system: error: exception thrown: #<condition &store-protocol-error [message: "build of `/gnu/store/l3kml1yk7ma9d1bybsjvv5iw1khy6b89-compute-guix-derivation.drv' failed" status: 100] 7f97fba2e540