Syntax and gexp for ff5f34ae757d709987896d6164bf125319a0f764

[Andreas Enge]

Hello,

it looks as if commit ff5f34ae757d709987896d6164bf125319a0f764 breaks
building of at least one package, perl-gd, depending on
perl-extutils-pkgconfig.

The latter is now defined as
(define-syntax perl-extutils-pkgconfig
  (identifier-syntax (perl-extutils-pkgconfig-for-target
                      (%current-target-system))))
which apparently does not play well with what is written in the former as
    (native-inputs
     (list perl-extutils-pkgconfig)) :
guix package: error: gnu/packages/gd.scm:103:2: package `perl-gd@2.73' has an 
invalid input: ("_" #<syntax-transformer perl-extutils-pkgconfig>)

I do not quite see where the problem lies, given that the same thing
has been working for pkg-config for quite a while now...
I noticed it on core-updates, but the commit comes from master.

Andreas