west: Renamed cmake.py to zcmake.py

Renamed cmake.py to zcmake.py to prevent import conflict if cmake is
installed through pip.

Signed-off-by: Jan Van Winkel <jan.van_winkel@dxplore.eu>
diff --git a/scripts/west_commands/build_helpers.py b/scripts/west_commands/build_helpers.py
index 63cdebc..a2bfb1b 100644
--- a/scripts/west_commands/build_helpers.py
+++ b/scripts/west_commands/build_helpers.py
@@ -10,7 +10,7 @@
 See build.py for the build command itself.
 '''
 
-import cmake
+import zcmake
 import os
 from west import log
 
@@ -51,7 +51,7 @@
     cache with a 'ZEPHYR_TOOLCHAIN_VARIANT' key.
     '''
     try:
-        cache = cmake.CMakeCache.from_build_dir(path)
+        cache = zcmake.CMakeCache.from_build_dir(path)
     except FileNotFoundError:
         cache = {}