scripts: zcmake: fix for prerelease cmake versions

Handle a semantic versioning case used by Kitware that is not
supported by the packaging module we're using for version comparisons.

Signed-off-by: Martí Bolívar <marti.bolivar@nordicsemi.no>
diff --git a/scripts/west_commands/zcmake.py b/scripts/west_commands/zcmake.py
index 353f766..bd1dc57 100644
--- a/scripts/west_commands/zcmake.py
+++ b/scripts/west_commands/zcmake.py
@@ -285,6 +285,10 @@
                 'Please install CMake ' + _MIN_CMAKE_VERSION_STR +
                 ' or higher (https://cmake.org/download/).')
     version = lines[0].split()[2]
+    if '-' in version:
+        # Handle semver cases like "3.19.20210206-g1e50ab6"
+        # which Kitware uses for prerelease versions.
+        version = version.split('-', 1)[0]
     if packaging.version.parse(version) < _MIN_CMAKE_VERSION:
         log.die('cmake version', version,
                 'is less than minimum version {};'.