🤖 fix: prevent unbound variable errors from system bashrc

Adds --norc to .SHELLFLAGS in Makefile to prevent bash from sourcing
/etc/bash.bashrc or ~/.bashrc during build commands.

This fixes an issue where system bashrc files containing strict checks
(like checking PS1 with set -u) would cause build failures or log spam
because make runs shells with -u (nounset).

Author: ammar-agent

Makefile

@@ -33,7 +33,7 @@ SHELL := bash
 else
 SHELL := /usr/bin/env bash
 endif
-.SHELLFLAGS := -eu -o pipefail -c
+.SHELLFLAGS := --norc -eu -o pipefail -c
 
 # Enable parallel execution by default (only if user didn't specify -j)
 ifeq (,$(filter -j%,$(MAKEFLAGS)))