Kconfig updates for v4.18
Kconfig now supports new functionality to perform textual substitution.
It has been a while since Linus suggested to move compiler option tests
from makefiles to Kconfig. Finally, here it is. The implementation has
been generalized into a Make-like macro language. Some built-in functions
such as 'shell' are provided. Variables and user-defined functions are
also supported so that 'cc-option', 'ld-option', etc. are implemented as
macros.
Summary:
- refactor package checks for building {m,n,q,g}conf
- remove unused/unmaintained localization support
- remove Kbuild cache
- drop CONFIG_CROSS_COMPILE support
- replace 'option env=' with direct variable expansion
- add built-in functions such as 'shell'
- support variables and user-defined functions
- add helper macros as as 'cc-option'
- add unit tests and a document of the new macro language
- add 'testconfig' to help
- fix warnings from GCC 8.1