To use any sanitizer(s), add it to the ENABLE_SANITIZERS list on
the CMake command line.
Examples:

cmake -GNinja .. -DENABLE_SANITIZERS=undefined
cmake -GNinja .. -DENABLE_SANITIZERS=address;leak

This requires an additional dependency to work:

ECM (Extra Cmake Modules, https://api.kde.org/ecm/index.html)

To install on Debian/Ubuntu:

sudo apt install extra-cmake-modules

This dependency is only required if the ENABLE_SANITIZERS variable
is set, it is not necessary to do a standard build.

The ECM package will check for compiler compatibility and set the
appropriated options for each sanitizer. It will eventually remove the
optimization options that may conflict with the selected sanitizers.

With ECM *not* installed:

mkdir buildcmake && cd buildcmake
cmake -GNinja ..
ninja

The build should be successful.

rm -rf *
cmake -GNinja .. -DENABLE_SANITIZERS=undefined

CMake should return en error:

ECM is required to enable the sanitizers

(https://api.kde.org/ecm/index.html)

Install ECM (instructions for Debian/Ubuntu):

sudo apt install extra-cmake-modules

Then

rm -rf *
cmake -GNinja .. -DENABLE_SANITIZERS=undefined
ninja -v

The build should enable the sanitizer (check the build commands for
-fsanitize=undefined)

rm -rf *
cmake -GNinja .. -DENABLE_SANITIZERS="address;leak"

Note: if you need to disable assembly instructions, add
-DUSE_ASM_X86_64=OFF to the CMake command line.

ninja -v

The build should enable the sanitizers (check the build commands for
-fsanitize=address and -fsanitize=leak)