Merge "Set MAKEFLAGS=-j and GTEST_BRIEF in .envrc" into main

.envrc

@@ -1,3 +1,9 @@
 # shellcheck shell=bash
 source_env_if_exists .envrc.local
+# TODO: `use flake .#native-clangStdenvPackages` on macOS?
 use flake ".#${LIX_SHELL_VARIANT:-default}" "${LIX_SHELL_EXTRA_ARGS[@]}"
+export MAKEFLAGS="$MAKEFLAGS -e"
+if [[ -n "$NIX_BUILD_CORES" ]]; then
+    export MAKEFLAGS="$MAKEFLAGS -j $NIX_BUILD_CORES"
+fi
+export GTEST_BRIEF=1

.gitignore

@@ -157,3 +157,5 @@ result-*
 
 # ClangBuildAnalyzer output, see maintainers/buildtime_report.sh
 buildtime.bin
+
+.envrc.local