Kconfig settings of string type is passed to CMake with quotes to ensure
they are properly handled, for example when specified in testcase.yml as
> extra_args:
> - CONFIG_FOO="bar"
Support sysbuild Kconfig settings `SB_CONFIG` by performing the same
quoting for settings starting with `SB_CONFIG_`.
Signed-off-by: Torsten Rasmussen <Torsten.Rasmussen@nordicsemi.no>
