Pass the --db-client option to sqitch deploy

So that it can always find psql.

configure.ac

@@ -36,6 +36,7 @@ AC_SUBST([guilemoduledir])
 AC_SUBST([GUILE_EFFECTIVE_VERSION])
 
 AC_PATH_PROG([sqitch], [sqitch])
+AC_PATH_PROG([psql], [psql])
 
 dnl Substitute placeholders to generate these target files
 AC_CONFIG_FILES([Makefile])

guix-data-service/config.scm.in

@@ -34,6 +34,7 @@
            (port        . 8765)
 
            (sqitch      . "@sqitch@")
+           (sqitch-psql . "@psql@")
            (sqitch-plan . ,(let ((installed-plan
                                   "@prefix@/share/guix-data-service/sqitch/sqitch.plan")
                                  (dev-plan

scripts/guix-data-service.in

@@ -71,6 +71,7 @@
     (let ((command
            (list (%config 'sqitch)
                  "deploy"
+                 "--db-client" (%config 'sqitch-psql)
                  "--plan-file" (%config 'sqitch-plan)
                  (string-append "db:pg://"
                                 (%config 'database-user)