build: wire merge-bin.py for the merged-image (full-install) target

Adds the portable merge-bin.py post-script (app-bin -> out/ + a 'mergebin' custom
target) and enables it in both touch envs. Each board now produces firmware.bin
(app/OTA slot) and firmware-merged.bin (full install @ 0x0) — the two artifacts a
release ships. Verified: V4 merged 2.66 MB, T-Deck merged 2.88 MB.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Signed-off-by: Kaj Schittecat <kaj@schittecat.com>

merge-bin.py

@@ -0,0 +1,110 @@
+#!/usr/bin/python3
+
+# Post-link: copy app .bin to out/<PIOENV>.bin and a timestamped copy; optional merge_bin target for merged flash image.
+
+import os
+import shutil
+import subprocess
+from datetime import datetime
+
+Import("env", "projenv")
+
+board_config = env.BoardConfig()
+firmware_bin = "${BUILD_DIR}/${PROGNAME}.bin"
+merged_bin = os.environ.get("MERGED_BIN_PATH", "${BUILD_DIR}/${PROGNAME}-merged.bin")
+
+
+def _git_short_sha(project_dir):
+    try:
+        r = subprocess.run(
+            ["git", "-C", project_dir, "rev-parse", "--short", "HEAD"],
+            capture_output=True,
+            text=True,
+            timeout=8,
+        )
+        sha = (r.stdout or "").strip()
+        if r.returncode != 0 or not sha:
+            return "nogit"
+        dirty = subprocess.run(
+            ["git", "-C", project_dir, "diff", "--quiet"],
+            timeout=8,
+            capture_output=True,
+        )
+        return sha + ("-dirty" if dirty.returncode != 0 else "")
+    except (OSError, subprocess.TimeoutExpired):
+        return "nogit"
+
+
+def _copy_one(src_path, dst_path):
+    shutil.copy2(src_path, dst_path)
+    print("Copied %s -> %s" % (src_path, dst_path))
+
+
+def _copy_to_out(env, src_path, out_suffix):
+    if not src_path or not os.path.isfile(src_path):
+        return
+    pioenv = env["PIOENV"]
+    project_dir = env["PROJECT_DIR"]
+    stamp = datetime.now().strftime("%Y%m%d_%H%M%S")
+    sha = _git_short_sha(project_dir)
+    stable_name = pioenv + out_suffix + ".bin"
+    stamped_name = "%s%s-%s-%s.bin" % (pioenv, out_suffix, stamp, sha)
+
+    out_dir = os.path.join(project_dir, "out")
+    os.makedirs(out_dir, exist_ok=True)
+    _copy_one(src_path, os.path.join(out_dir, stable_name))
+    _copy_one(src_path, os.path.join(out_dir, stamped_name))
+
+    # When the project lives in a subfolder (e.g. HeltecV4/MeshCore), also copy to <workspace>/out
+    parent_out = os.path.normpath(os.path.join(project_dir, "..", "out"))
+    if parent_out != os.path.normpath(out_dir):
+        try:
+            os.makedirs(parent_out, exist_ok=True)
+            _copy_one(src_path, os.path.join(parent_out, stable_name))
+            _copy_one(src_path, os.path.join(parent_out, stamped_name))
+        except OSError as exc:
+            print("Note: could not mirror to parent out/: %s" % exc)
+
+
+def copy_app_bin_to_out(target, source, env):
+    bin_path = os.path.join(env.subst("$BUILD_DIR"), env.subst("${PROGNAME}") + ".bin")
+    _copy_to_out(env, bin_path, "")
+
+
+def merge_bin_action(source, target, env):
+    flash_images = [
+        *env.Flatten(env.get("FLASH_EXTRA_IMAGES", [])),
+        "$ESP32_APP_OFFSET",
+        source[0].get_abspath(),
+    ]
+    merge_cmd = " ".join(
+        [
+            '"$PYTHONEXE"',
+            '"$OBJCOPY"',
+            "--chip",
+            board_config.get("build.mcu", "esp32"),
+            "merge_bin",
+            "-o",
+            merged_bin,
+            "--flash_mode",
+            board_config.get("build.flash_mode", "dio"),
+            "--flash_freq",
+            "${__get_board_f_flash(__env__)}",
+            "--flash_size",
+            board_config.get("upload.flash_size", "4MB"),
+            *flash_images,
+        ]
+    )
+    env.Execute(merge_cmd)
+
+
+env.AddPostAction("$BUILD_DIR/${PROGNAME}.bin", copy_app_bin_to_out)
+
+env.AddCustomTarget(
+    name="mergebin",
+    dependencies=firmware_bin,
+    actions=merge_bin_action,
+    title="Merge binary",
+    description="Build combined image",
+    always_build=True,
+)

platformio.ini

@@ -14,7 +14,7 @@ framework = arduino
 board = heltec_v4
 monitor_speed = 115200
 board_build.partitions = partitions_tft_touch.csv
-extra_scripts = pre:scripts/inject_wifi_env.py
+extra_scripts = pre:scripts/inject_wifi_env.py, merge-bin.py
 
 build_flags =
   -w -DNDEBUG -DRADIOLIB_STATIC_ONLY=1 -DRADIOLIB_GODMODE=1
@@ -206,7 +206,7 @@ framework = arduino
 board = t-deck
 monitor_speed = 115200
 board_build.partitions = variants/lilygo_tdeck/partitions_tdeck_touch.csv
-extra_scripts = pre:scripts/inject_wifi_env.py
+extra_scripts = pre:scripts/inject_wifi_env.py, merge-bin.py
 
 build_flags =
   -w -DNDEBUG -DRADIOLIB_STATIC_ONLY=1 -DRADIOLIB_GODMODE=1