in the initial impl, the regex is depends on ALLOW_MIT_COMPONENTS, and
if other modules want to use regex, also needs to depends on
ALLOW_MIT_COMPONENTS, which is ambiguity, so we provide a seperate
kconfig option for regex: LIBC_REGEX, which is depends on
ALLOW_MIT_COMPONENTS, but is enabled by default. Thus if
ALLOW_MIT_COMPONENTS is enabled, then the LIBC_REGEX is also enabled
either automatically, and this is more clear than controlled by
ALLOW_MIT_COMPONENTS option only.
Signed-off-by: guoshichao <guoshichao@xiaomi.com>
xuxin19