The build system includes its one check for available CMake build types.
This check is incorrect as it doesn't include the None build type.

diff -upr ettercap-0.8.3.orig/CMakeLists.txt ettercap-0.8.3/CMakeLists.txt
--- ettercap-0.8.3.orig/CMakeLists.txt	2020-02-22 11:43:41.543886679 +0100
+++ ettercap-0.8.3/CMakeLists.txt	2020-02-22 11:43:57.684103657 +0100
@@ -22,7 +22,7 @@ option(LIBRARY_BUILD "Build for libetter
 option(INSTALL_DESKTOP "Install ettercap desktop files" ON)
 
 
-set(VALID_BUILD_TYPES Debug Release RelWithDebInfo)
+set(VALID_BUILD_TYPES None Debug Release RelWithDebInfo)
 
 if(NOT CMAKE_BUILD_TYPE)
   # Default to using "Release" as our build type.