* The `CMAKE_BUILD_TYPE=None` option is commonly used to respect the
user's optimization flags. Users may be interested in enabling LTO
anyway in that case. Implement this the Debian build.
* Remove typo, the value is called RelWithDebInfo. Enable LTO for this
by default.
[Minor] Make ragel-generated files independent of the parent directory
* Use relative paths for `#line` directives to allow reproducible builds
independent of the absolute build directory. For /b/rspamd/src/x.rl
and build dir /b/build, it could result in `../../build/src/x.rl`.
* The `-L` option for `Inhibit writing #line directives` is useless, it
just comments out the line with `/* ... */`, but that means that the
source file is still different.
* Note that ragel only accepts one input file, despite plural `INPUTS`.
[Minor] do not pass invalid C warnings to C++ flags
cc1plus: warning: command line option ‘-Wno-pointer-sign’ is valid for C/ObjC but not for C++
cc1plus: warning: command line option ‘-Wstrict-prototypes’ is valid for C/ObjC but not for C++
ENABLE_OPENBLAS is removed because it was not used to check if the
openblas library should be used. The ENABLE_BLAS is moved from
CMakeLists.txt to cmake/Openblas.cmake to have all related variables in
one file and to reduce a complexity of CMakeLists.txt slightly.