Support Guile 3.0.

* configure.ac (GUILE_PKG): Add '3.0'.
* guix.scm: Use 'guile-3.0' for the Gash package.

configure.ac

@@ -25,7 +25,7 @@ AC_CONFIG_AUX_DIR([build-aux])
 AM_INIT_AUTOMAKE([color-tests silent-rules -Wall -Werror])
 AM_SILENT_RULES([yes])
 
-GUILE_PKG([2.2 2.0])
+GUILE_PKG([3.0 2.2 2.0])
 GUILE_PROGS
 
 AC_ARG_VAR([GUILD], [guild (Guile compiler) command])

guix.scm

@@ -90,7 +90,7 @@
      ("pkg-config" ,pkg-config)
      ("texinfo" ,texinfo)))
   (inputs
-   `(("guile" ,guile-2.2)))
+   `(("guile" ,guile-3.0)))
   (home-page "https://savannah.nongnu.org/projects/gash/")
   (synopsis "POSIX-compatible shell written in Guile Scheme")
   (description "Gash is a POSIX-compatible shell written in Guile