Fixes to eng specification for proper dir and non-bash shells.

The latter is needed for Github CI.

Author: kquick

_eng_/dev.eng

@@ -22,14 +22,15 @@ dev
         exec = nix build --no-link .#brick-panes.ghc912
     nixbuild:old
       Uses nix to build with old GHC versions
+        in dir = {TopDir}
         exec =
           nix build --no-link --override-input nixpkgs github:nixos/nixpkgs/25.05 $(
            for X in 810 90 92 ; do echo ".#brick-panes.ghc$X"; done)
-    nixbuild:recent
+    bp:nixbuild:recent
       Uses nix to build with old GHC versions
+        in dir = {TopDir}
         exec =
-          declare -a ghcvers=(94 96 98 910 912)
-          nix build --no-link ${ghcvers[*]/#/.#brick-panes.ghc}
+          nix build --no-link $(for X in 94 96 98 910 912; do echo ".#brick-panes.ghc$X"; done)
     nixbuild:all
       Uses nix to build with all supported GHC versions
         needs = nixbuild nixbuild:old nixbuild:recent