Improve setting the default chroot dirs

release.nix

@@ -93,13 +93,6 @@ let
           --sysconfdir=/etc
         '';
 
-        # Provide a default value for the ‘build-chroot-dirs’ setting
-        # that includes /bin/sh pointing to bash.
-        preHook = lib.optionalString stdenv.isLinux
-          ''
-            export DEFAULT_CHROOT_DIRS="/bin/sh=${stdenv.shell}"
-          '';
-
         enableParallelBuilding = true;
 
         makeFlags = "profiledir=$(out)/etc/profile.d";

src/libstore/build.cc

@@ -1784,9 +1784,14 @@ void DerivationGoal::startBuilder()
     }
 
     if (useChroot) {
+
+        string defaultChrootDirs;
+        if (isInStore(BASH_PATH))
+            defaultChrootDirs = "/bin/sh=" BASH_PATH;
+
         /* Allow a user-configurable set of directories from the
            host file system. */
-        PathSet dirs = tokenizeString<StringSet>(settings.get("build-chroot-dirs", string(DEFAULT_CHROOT_DIRS)));
+        PathSet dirs = tokenizeString<StringSet>(settings.get("build-chroot-dirs", defaultChrootDirs));
         PathSet dirs2 = tokenizeString<StringSet>(settings.get("build-extra-chroot-dirs", string("")));
         dirs.insert(dirs2.begin(), dirs2.end());
 

src/libstore/local.mk

@@ -22,7 +22,7 @@ libstore_CXXFLAGS = \
  -DNIX_CONF_DIR=\"$(sysconfdir)/nix\" \
  -DNIX_LIBEXEC_DIR=\"$(libexecdir)\" \
  -DNIX_BIN_DIR=\"$(bindir)\" \
- -DDEFAULT_CHROOT_DIRS="\"$(DEFAULT_CHROOT_DIRS)\""
+ -DBASH_PATH="\"$(bash)\""
 
 $(d)/local-store.cc: $(d)/schema.sql.hh