CMSIS Pack: Use pdsc-relative path for resource files, fixes pyocd#1460

This patch will try to read resource files (e.g. FLMs) using
relative path to the pdsc file, which is used when some hardware vendors
places their pdscs under subdirectory of a pack archive, and somehow
valid for Keil MDK.

Signed-off-by: Yilin Sun <imi415@imi.moe>

pyocd/target/pack/cmsis_pack.py

@@ -129,6 +129,13 @@ def get_file(self, filename) -> IO[bytes]:
             opened (due to particularities of the ZipFile implementation).
         """
         filename = filename.replace('\\', '/')
+
+        # Some vendors place their pdsc in some subdirectories of the pack archive,
+        # use relative directory to the pdsc file while reading other files.
+        pdsc_base = self._pdscName.rsplit('/', 1)
+        if len(pdsc_base) == 2:
+            filename = f'{pdsc_base[0]}/{filename}'
+
         return io.BytesIO(self._pack_file.read(filename))
 
 class CmsisPackDescription: