feat(tvix): Add scripts for local nix daemon testing

These are the scripts I use to test the nix daemon interaction with a
non-/nix store directory during development, copied almost verbatim from
my cmake build directory. As such, there's likely a *lot* of cleanup and
deduplication to be done here, but I'm committing these as is in the
hope that others can benefit from them somehow.

Change-Id: I42a10a85e6731fa2014c7ea9738224d678a8376b
Reviewed-on: https://cl.tvl.fyi/c/depot/+/1881
Reviewed-by: kanepyork <rikingcoding@gmail.com>
Tested-by: BuildkiteCI

third_party/nix/scripts/daemon.sh

@@ -0,0 +1,24 @@
+#!/usr/bin/env bash
+set -eo pipefail
+
+# Run a nix daemon using a local store, for use during development. Intended to
+# be run from the cmake build directory
+
+if [ $1 = "--debug" ]; then
+    run=(gdb --args)
+    shift 1
+elif [ "$1" = "--rr" ]; then
+    run=(rr record)
+    shift 1
+else
+    run=()
+fi
+
+make -j 10
+NIX_STORE_DIR=$(pwd)/nix/store \
+    NIX_LOG_DIR=$(pwd)/nix/var/log/nix \
+    NIX_STATE_DIR=$(pwd)/nix/var/nix \
+    XDG_CACHE_HOME=$(pwd)/cache \
+    NIX_LIBEXEC_DIR=$(pwd) \
+    GRPC_TRACE=all \
+    ${gdb[*]} ./src/nix-daemon/nix-daemon