CMake: Do not map all unknown build target types to "ExecutableType"

There is UtilityType now, so use that if there is no executable being
generated.

Change-Id: I9e8d512077b8352ec056b49c8db03644482b8fbc
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

src/plugins/cmakeprojectmanager/cmakeproject.cpp

@@ -762,7 +762,7 @@ void CMakeBuildTarget::clear()
     workingDirectory.clear();
     sourceDirectory.clear();
     title.clear();
-    targetType = ExecutableType;
+    targetType = UtilityType;
     includeFiles.clear();
     compilerOptions.clear();
     defines.clear();