CMake: Centralize target linkage in source/CMakeLists.txt

This refactors the CMake layout so that the top-level CMakeLists.txt is limited
to project configuration: options, feature resolution, platform/compiler setup,
and package discovery.

Target construction and linkage are centralized in source/CMakeLists.txt, which
now owns:

- the common linear-algebra dependency interface;
- optional external feature dependencies;
- the final external link closure;
- the ABACUS executable and its ordered internal target linkage;
- unit-test setup and registration of the top-level integration tests.

The final link closure is kept in one explicit location. Its order is part of
the build contract, especially for static or mixed static/shared builds:

1. internal ABACUS targets, from higher-level consumers to lower-level
   providers;
2. optional external feature libraries;
3. numerical backends and their MPI, OpenMP, compiler-runtime, and system
   dependencies.

Dependencies are therefore no longer accumulated through the legacy
`${math_libs}` path or scattered between the root CMakeLists.txt, test
directories, and setup modules. The old global OpenMP flag/link-option handling
is also removed in favour of imported targets and their usage requirements.

The top-level integration-test directory is registered only after the final
executable and its path are available. No integration-test cases are changed.

This is a structural cleanup only. It does not redesign dependency discovery or
change the current provider-selection logic for MKL, cuSOLVERMp, PEXSI, ELPA,
FFTW, ScaLAPACK, KML, or GPU dependencies, part of which need to be revised
seperately .

Author: Growl1234

CMakeLists.txt

@@ -7,7 +7,7 @@
 function(setup_build_info)
     message(STATUS "Setting up build information...")
 
-    include(cmake/CollectBuildInfoVars.cmake)
+    include(${PROJECT_SOURCE_DIR}/cmake/CollectBuildInfoVars.cmake)
 
 set(BUILD_INFO_TEMPLATE "${CMAKE_SOURCE_DIR}/source/source_io/build_info.h.in")
 set(BUILD_INFO_OUTPUT   "${CMAKE_BINARY_DIR}/source/source_io/build_info.h")

cmake/BuildInfo.cmake

@@ -4,7 +4,7 @@
 
 include_guard(GLOBAL)
 
-function(abacus_setup_cublasmp target_name)
+function(abacus_setup_cublasmp)
   abacus_add_feature_definitions(__CUBLASMP)
 
   # 1. Search for cuBLASMp library and header files
@@ -72,7 +72,4 @@ function(abacus_setup_cublasmp target_name)
         INTERFACE_INCLUDE_DIRECTORIES "${CUBLASMP_INCLUDE_DIR}")
   endif()
 
-  # 5. Propagate library usage requirements to all ABACUS targets.
-  target_link_libraries(abacus_external_deps INTERFACE cublasMp::cublasMp)
-
 endfunction()

cmake/SetupCuBlasMp.cmake

@@ -4,7 +4,7 @@
 
 include_guard(GLOBAL)
 
-function(abacus_setup_cusolvermp target_name)
+function(abacus_setup_cusolvermp)
   abacus_add_feature_definitions(__CUSOLVERMP)
 
   # Find cuSOLVERMp first, then decide communicator backend.
@@ -126,10 +126,4 @@ function(abacus_setup_cusolvermp target_name)
         INTERFACE_INCLUDE_DIRECTORIES "${CUSOLVERMP_INCLUDE_DIR}")
   endif()
 
-  # === Link libraries and propagate include directories ===
-  if(_use_cal)
-    target_link_libraries(abacus_external_deps INTERFACE CAL::CAL cusolverMp::cusolverMp)
-  else()
-    target_link_libraries(abacus_external_deps INTERFACE NCCL::NCCL cusolverMp::cusolverMp)
-  endif()
 endfunction()

cmake/SetupCuSolverMp.cmake

@@ -2,7 +2,7 @@ include_guard(GLOBAL)
 
 include(CheckIncludeFileCXX)
 
-function(abacus_setup_nccl target_name)
+function(abacus_setup_nccl)
   find_library(NCCL_LIBRARY NAMES nccl
       HINTS ${NCCL_PATH} ${NVHPC_ROOT_DIR}
       PATH_SUFFIXES lib lib64 comm_libs/nccl/lib)
@@ -39,5 +39,4 @@ function(abacus_setup_nccl target_name)
     endif()
   endif()
 
-  target_link_libraries(abacus_external_deps INTERFACE NCCL::NCCL)
 endfunction()

cmake/SetupNccl.cmake

@@ -39,16 +39,16 @@ endif()
     endif()
 
     # dependencies & link library
-    target_link_libraries(${UT_TARGET} PRIVATE ${UT_LIBS} Threads::Threads
-                          GTest::gtest_main GTest::gmock_main)
+    target_link_libraries(${UT_TARGET} PRIVATE
+      ${UT_LIBS}
+      GTest::gtest_main
+      GTest::gmock_main
+      abacus::link_libs)
     if(ENABLE_GOOGLEBENCH)
       target_link_libraries(
         ${UT_TARGET} PRIVATE benchmark::benchmark)
     endif()
 
-    if(USE_OPENMP)
-      target_link_libraries(${UT_TARGET} PRIVATE OpenMP::OpenMP_CXX)
-    endif()
 
     # Link to build info if needed
     if("${UT_SOURCES}" MATCHES "parse_args.cpp")
@@ -64,7 +64,6 @@ endif()
 
 if(BUILD_TESTING)
   set_if_higher(CMAKE_CXX_STANDARD 14) # Required in orbital
-  include(CTest)
   enable_testing()
   find_package(GTest HINTS /usr/local/lib/ ${GTEST_DIR})
   if(NOT ${GTest_FOUND})
@@ -79,5 +78,4 @@ if(BUILD_TESTING)
   endif()
   # TODO: Try the GoogleTest module.
   # https://cmake.org/cmake/help/latest/module/GoogleTest.html
-  add_subdirectory(tests) # Contains integration tests
 endif()