assemble.py: don't read BOARD.dts.pre.tmp

This file has been removed from upstream Zephyr in commit 2b7c61e306a
("cmake: re-work devicetree preprocessing steps").

Get the board name from .config instead; this is a stable place for it
to be found. Load the EDT itself from the pickle file in the build
directory; this has the advantage of fixing the script when out of
tree devicetree bindings are used.

Signed-off-by: Martí Bolívar <marti.bolivar@nordicsemi.no>

scripts/assemble.py

@@ -26,6 +26,7 @@ import io
 import re
 import os
 import os.path
+import pickle
 import sys
 
 def same_keys(a, b):
@@ -95,13 +96,12 @@ class Assembly():
             ofd.write(ibuf)
 
 def find_board_name(bootdir):
-    suffix = ".dts.pre.tmp"
-
-    for _, _, files in os.walk(os.path.join(bootdir, "zephyr")):
-        for filename in files:
-            if filename.endswith(suffix):
-                return filename[:-len(suffix)]
-
+    dot_config = os.path.join(bootdir, "zephyr", ".config")
+    with open(dot_config, "r") as f:
+        for line in f:
+            if line.startswith("CONFIG_BOARD="):
+                return line.split("=", 1)[1].strip('"')
+    raise Exception("Expected CONFIG_BOARD line in {}".format(dot_config))
 
 def main():
     parser = argparse.ArgumentParser()
@@ -132,10 +132,10 @@ def main():
 
     board = find_board_name(args.bootdir)
 
-    dts_path = os.path.join(args.bootdir, "zephyr", board + ".dts.pre.tmp")
-
-    edt = devicetree.edtlib.EDT(dts_path, [os.path.join(zephyr_base, "dts", "bindings")],
-            warn_reg_unit_address_mismatch=False)
+    edt_pickle = os.path.join(args.bootdir, "zephyr", "edt.pickle")
+    with open(edt_pickle, 'rb') as f:
+        edt = pickle.load(f)
+        assert isinstance(edt, devicetree.edtlib.EDT)
 
     output = Assembly(args.output, args.bootdir, edt)