west: Load CMakeCache.txt as a UTF-8 encoded file

CMake has been using UTF-8 as an encoding for CMakeCache.txt since 3.2.

Fixes #17635

Signed-off-by: Carles Cufi <carles.cufi@nordicsemi.no>
diff --git a/scripts/west_commands/zcmake.py b/scripts/west_commands/zcmake.py
index 85e0b8d..afc1366 100644
--- a/scripts/west_commands/zcmake.py
+++ b/scripts/west_commands/zcmake.py
@@ -213,7 +213,7 @@
 
     def load(self, cache_file):
         entries = []
-        with open(cache_file, 'r') as cache:
+        with open(cache_file, 'r', encoding="utf-8") as cache:
             for line_no, line in enumerate(cache):
                 entry = CMakeCacheEntry.from_line(line, line_no)
                 if entry: