fix(e2e): default native_sim/native/64 for Zephyr (avoid -m32 multilib)

First run failed on x86_64 without 32-bit libgcc; Zephyr documents LP64 variant.
Validated: west build + gdbserver -> rsgdb -> gdb batch OK.

Made-with: Cursor

Author: Alex J Lennon

CONTRIBUTING.md

@@ -67,7 +67,7 @@ RUN_E2E_GDB=1 ./scripts/validate_local.sh
 
 To debug a **real Zephyr app** (still RSP/gdbserver) without QEMU or hardware, build for the **`native_sim`** board: Zephyr links a normal Linux executable (`zephyr.exe`). Flow matches CI: **gdbserver → rsgdb → GDB**.
 
-Requires a full [Zephyr west workspace](https://docs.zephyrproject.org/latest/develop/getting_started/index.html) (`ZEPHYR_WORKSPACE` with `.west/` and `zephyr/`). See [native_sim](https://docs.zephyrproject.org/latest/boards/native/native_sim/doc/index.html).
+Requires a full [Zephyr west workspace](https://docs.zephyrproject.org/latest/develop/getting_started/index.html) (`ZEPHYR_WORKSPACE` with `.west/` and `zephyr/`). See [native_sim](https://docs.zephyrproject.org/latest/boards/native/native_sim/doc/index.html). The script builds **`native_sim/native/64`** by default (LP64 host binary); the plain `native_sim` target is 32-bit and needs multilib on x86_64.
 
 ```bash
 export ZEPHYR_WORKSPACE=/path/to/zephyrproject

README.md

@@ -200,7 +200,7 @@ cargo test
 # cargo build --release && ./scripts/e2e_gdb_smoke.sh
 # Or: RUN_E2E_GDB=1 ./scripts/validate_local.sh
 #
-# Optional: Zephyr native_sim (Linux ELF) — needs ZEPHYR_WORKSPACE; see CONTRIBUTING.md
+# Optional: Zephyr native_sim (Linux ELF) — needs ZEPHYR_WORKSPACE; default board is native_sim/native/64
 # ./scripts/e2e_zephyr_native_sim.sh
 # Or: RUN_E2E_ZEPHYR_NATIVE=1 ./scripts/validate_local.sh
 

scripts/e2e_zephyr_native_sim.sh

@@ -14,6 +14,7 @@
 #
 # Optional:
 #   ZEPHYR_APP=zephyr/samples/hello_world   (path relative to workspace root)
+#   ZEPHYR_BOARD=native_sim/native/64       (default: 64-bit LP64 — works on typical x86_64 Linux without gcc-multilib)
 #   RSGDB, GDB_PORT, PROXY_PORT — same as e2e_gdb_smoke.sh
 #
 # CI: not run by default (heavy); set RUN_E2E_ZEPHYR_NATIVE=1 in validate_local.sh locally.
@@ -53,17 +54,19 @@ if ! command -v gcc >/dev/null 2>&1 && ! command -v clang >/dev/null 2>&1; then
 fi
 
 ZEPHYR_APP="${ZEPHYR_APP:-zephyr/samples/hello_world}"
+# Default board is 64-bit native_sim so linking does not require 32-bit multilib (-m32 + libgcc).
+ZEPHYR_BOARD="${ZEPHYR_BOARD:-native_sim/native/64}"
 WORKDIR="$(mktemp -d)"
 trap 'rm -rf "$WORKDIR"; kill ${RSGDB_PID:-0} ${GDBSERVER_PID:-0} 2>/dev/null || true' EXIT
 
 GDB_PORT="${GDB_PORT:-13335}"
 PROXY_PORT="${PROXY_PORT:-13336}"
 BUILD_DIR="$WORKDIR/native_sim_build"
 
-echo "==> west build -b native_sim (first run can take several minutes)"
+echo "==> west build -b $ZEPHYR_BOARD (first run can take several minutes)"
 (
   cd "$ZEPHYR_WORKSPACE"
-  west build -b native_sim -p auto -d "$BUILD_DIR" "$ZEPHYR_APP" -- \
+  west build -b "$ZEPHYR_BOARD" -p auto -d "$BUILD_DIR" "$ZEPHYR_APP" -- \
     -DCONFIG_NO_OPTIMIZATIONS=y
 )