ADD: fmt as private library

Context

Link fmt library to target to avoid linkage error with Python library.

CMakeLists.txt

@@ -85,17 +85,6 @@ endif()
 
 # ##############################################
 # Find system dependencies
-Include(FetchContent)
-
-FetchContent_Declare(
-    fmt
-    GIT_REPOSITORY https://github.com/fmtlib/fmt.git
-    GIT_TAG        10.2.1 # or a later release
-)
-
-set(FMT_SYSTEM_HEADERS ON)
-FetchContent_MakeAvailable(fmt)
-set_property(TARGET fmt PROPERTY POSITION_INDEPENDENT_CODE ON)
 
 if(CUDA)
     find_package(CUDAToolkit REQUIRED)
@@ -169,7 +158,7 @@ if (PYBIND)
 endif()
 
 # XXX HERE !!!
-target_link_libraries(${module_name} PUBLIC fmt::fmt)
+target_link_libraries(${module_name} PRIVATE fmt::fmt)
 target_compile_features(${module_name} PRIVATE cxx_std_14)
 
 target_compile_options(${module_name} PRIVATE