A design flaw of 'gsource' is that there's no way to require at least
one file to match the glob pattern. This could lead to silent errors.
Switch to a new design, where a plain 'source' is globbing and requires
at least one file to match. A separate 'osource' (optional source)
statement is available for cases where it's okay for a pattern (or plain
filename) to not match any files.
'orsource' combines 'osource' and 'rsource' (relative source).
This commit search-replaces 'gsource' with 'source', but backwards
compatibility with 'gsource' is still maintained by making it an alias
for 'osource' (and by making 'grsource' an alias for 'orsource').
The three Kconfig files arch/{nios2,posix,xtensa}/Kconfig source
arch/{nios2,posix,xtensa}/soc/*/Kconfig, which doesn't match any files.
Use 'osource' for those. The soc/*/Kconfig files seem to be for
additional SoC-specific symbols, only none exist yet on those ARCHes.
Also use 'osource' for the source of $ENV_VAR_BOARD_DIR/Kconfig in
boards/Kconfig, which doesn't exist for all boards.
Signed-off-by: Ulf Magnusson <Ulf.Magnusson@nordicsemi.no>