[BUG] Configuration vs. compilation guard mismatch

[juan131]

Describe the bug

As we can see in the svs.cmake, SVS isn't supported with GCC < 11:

# GCC < v11 does not support C++20 features required for SVS
# https://gcc.gnu.org/projects/cxx-status.html
if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
    if(CMAKE_CXX_COMPILER_VERSION VERSION_LESS "11.0")
        set(SVS_SUPPORTED 0)
        message(STATUS "Skipping SVS: requires GCC >= 11.")
    endif()
endif()

However, the SVS source files are added and they unconditionally include SVS headers regardless CMake detects GCC < 11.

To Reproduce

Steps to reproduce the behavior:

On a distro with GCC < 11 (e.g. Debian 11), run:

$ make (...)
(...)
-- Skipping SVS: requires GCC >= 11.
-- SVS support disabled
(...)
[ 30%] Building CXX object src/VecSim/CMakeFiles/VectorSimilarity.dir/index_factories/tiered_factory.cpp.o
[ 30%] Building CXX object src/VecSim/CMakeFiles/VectorSimilarity.dir/index_factories/index_factory.cpp.o
In file included from /modules/redisearch/src/deps/VectorSimilarity/src/VecSim/algorithms/svs/svs_tiered.h:5,
                 from /modules/redisearch/src/deps/VectorSimilarity/src/VecSim/index_factories/tiered_factory.h:16,
                 from /modules/redisearch/src/deps/VectorSimilarity/src/VecSim/index_factories/index_factory.cpp:13:
/modules/redisearch/src/deps/VectorSimilarity/src/VecSim/algorithms/svs/svs.h:21:10: fatal error: svs/index/vamana/dynamic_index.h: No such file or directory
   21 | #include "svs/index/vamana/dynamic_index.h"
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
compilation terminated.
In file included from /modules/redisearch/src/deps/VectorSimilarity/src/VecSim/algorithms/svs/svs_tiered.h:5,
                 from /modules/redisearch/src/deps/VectorSimilarity/src/VecSim/index_factories/tiered_factory.h:16,
                 from /modules/redisearch/src/deps/VectorSimilarity/src/VecSim/index_factories/tiered_factory.cpp:9:
/modules/redisearch/src/deps/VectorSimilarity/src/VecSim/algorithms/svs/svs.h:21:10: fatal error: svs/index/vamana/dynamic_index.h: No such file or directory
   21 | #include "svs/index/vamana/dynamic_index.h"
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
compilation terminated. 

Expected behavior

Compilation should work disabling SVS.

Environment (please complete the following information):

• OS: Debian 11
• Version/branch: latest