Warn if a symbol with unsatisfied deps is selected

Mirrors a warning in the C implementation. Make it a bit more
informative and simpler to decode for people who aren't super familiar
with Kconfig.

The warning is printed when/if the symbol is evaluated, e.g. when
writing a .config or C header or accessing Symbol.str/tri_value. It is
not printed if the symbol value has already been calculated and is
cached and up-to-date, which avoids warning spam.

Example:

  config Y_SYMBOL_1
  	def_bool y

  config Y_SYMBOL_2
  	def_bool y

  config SELECTED
  	bool
  	depends on !Y_SYMBOL_1

  config SELECTING_1
  	def_bool y
  	select SELECTED

  # Skipped in warning, because n
  config SELECTING_2
  	def_bool n
  	select SELECTED

  config SELECTING_3
  	def_bool y
  	select SELECTED if Y_SYMBOL_1
  	depends on Y_SYMBOL_2

  # Defined in multiple locations
  config SELECTING_3

Generated warning:

  warning: SELECTED (defined at Kconfig:7) has unsatisfied direct dependencies (!Y_SYMBOL_1), but is currently being selected by the following symbols:
  SELECTING_3 (value: y, defined at Kconfig:20, Kconfig:26), with direct dependencies "y" (value: y) and select condition Y_SYMBOL_1 && Y_SYMBOL_2 (value: y)
  SELECTING_1 (value: y, defined at Kconfig:11), with direct dependencies "y" (value: y)

Real-world example from test suite:

  warning: NOT_COHERENT_CACHE (defined at arch/powerpc/platforms/Kconfig.cputype:381) has unsatisfied direct dependencies (4xx || PPC_8xx || E200 || PPC_MPC512x || GAMECUBE_COMMON), but is currently being selected by the following symbols:
  AMIGAONE (value: y, defined at arch/powerpc/platforms/amigaone/Kconfig:2), with direct dependencies 6xx && BROKEN_ON_SMP (value: y) and select condition 6xx && BROKEN_ON_SMP (value: y)

0 files changed, 0 insertions, 0 deletions