Don't use whoami

`whoami` doesn't work when auto-uid-allocation is enabled and
sandboxing is disabled, since then the build UID doesn't have a
matching entry in /etc/passwd.

src/nix/daemon.cc

@@ -181,7 +181,6 @@ static bool matchUser(std::optional<uid_t> uid, std::optional<gid_t> gid, const
 
         if (gid) {
             auto gr = getgrgid(gid.value());
-            //std::string group = gr ? gr->gr_name : std::to_string(peer.gid.value());
 
             /* Don't allow connecting as the build users group. */
             if (gr && gr->gr_name == settings.buildUsersGroup)

tests/functional/bash-profile.sh

@@ -2,8 +2,7 @@ source common.sh
 
 sed -e "s|@localstatedir@|$TEST_ROOT/profile-var|g" -e "s|@coreutils@|$coreutils|g" < ../../scripts/nix-profile.sh.in > $TEST_ROOT/nix-profile.sh
 
-user=$(whoami)
 rm -rf $TEST_HOME $TEST_ROOT/profile-var
 mkdir -p $TEST_HOME
-USER=$user $SHELL -e -c ". $TEST_ROOT/nix-profile.sh; set"
-USER=$user $SHELL -e -c ". $TEST_ROOT/nix-profile.sh" # test idempotency
+USER=foobar $SHELL -e -c ". $TEST_ROOT/nix-profile.sh; set"
+USER=foobar $SHELL -e -c ". $TEST_ROOT/nix-profile.sh" # test idempotency

tests/functional/init.sh

@@ -26,7 +26,7 @@ substituters =
 flake-registry = $TEST_ROOT/registry.json
 show-trace = true
 include nix.conf.extra
-trusted-users = $(whoami)
+trusted-users = $(id -u)
 EOF
 
 cat > "$NIX_CONF_DIR"/nix.conf.extra <<EOF