This makes the target location consistent with other auto-generated
files like config_formats.h, config_core.h, and config_functions.h and
simplifies the build of clickhouse_common.
It can be useful to match versions, since in some tables
(system.trace_log) there is only revision column.
P.S. came to this when was digging into stress reports from CI.
P.P.S. case insensitive by analogy with version().
Signed-off-by: Azat Khuzhin <a.khuzhin@semrush.com>
cmake/target.cmake defines macros for the supported platforms, this
commit changes predefined system macros to our own macros.
__linux__ --> OS_LINUX
__APPLE__ --> OS_DARWIN
__FreeBSD__ --> OS_FREEBSD
