chore: Use find_package in CMake, fallback to fetch_content

CMakeLists.txt

@@ -5,7 +5,7 @@ file(STRINGS "${CMAKE_SOURCE_DIR}/version.txt" version)
 
 project(aidge_core
         VERSION ${version}
-        DESCRIPTION "Core algorithms for operators and graph of the AIDGE framework" 
+        DESCRIPTION "Core algorithms for operators and graph of the AIDGE framework"
         LANGUAGES CXX)
 message(STATUS "Project name: ${CMAKE_PROJECT_NAME}")
 message(STATUS "Project version: ${version}")
@@ -36,22 +36,28 @@ endif()
 
 ##############################################
 # Find system dependencies
-Include(FetchContent)
-
 set(FMT_VERSION 10.2.1)
-message(STATUS "Retrieving fmt ${FMT_VERSION} from git")
-FetchContent_Declare(
-    fmt
-    GIT_REPOSITORY https://github.com/fmtlib/fmt.git
-    GIT_TAG        ${FMT_VERSION} # or a later release
-)
 
-set(FMT_SYSTEM_HEADERS ON)
-FetchContent_MakeAvailable(fmt)
-set_property(TARGET fmt PROPERTY POSITION_INDEPENDENT_CODE ON)
+find_package(fmt ${FMT_VERSION} QUIET)
 
-find_package(Threads REQUIRED)
+if(NOT fmt_FOUND)
+    message(STATUS "fmt not found in system, retrieving from git")
+    Include(FetchContent)
+
+    FetchContent_Declare(
+        fmt
+        GIT_REPOSITORY https://github.com/fmtlib/fmt.git
+        GIT_TAG        ${FMT_VERSION}
+    )
 
+    set(FMT_SYSTEM_HEADERS ON)
+    FetchContent_MakeAvailable(fmt)
+    set_property(TARGET fmt PROPERTY POSITION_INDEPENDENT_CODE ON)
+else()
+    message(STATUS "Found system fmt version ${fmt_VERSION}")
+endif()
+
+find_package(Threads REQUIRED)
 ##############################################
 # Create target and set properties
 

unit_tests/CMakeLists.txt

-Include(FetchContent)
+find_package(Catch2 3.0.1)
 
-FetchContent_Declare(
-  Catch2
-  GIT_REPOSITORY https://github.com/catchorg/Catch2.git
-  GIT_TAG        v3.0.1 # or a later release
-)
+if(NOT Catch2_FOUND)
+    message(STATUS "Catch2 not found in system, retrieving from git")
+    Include(FetchContent)
 
-FetchContent_MakeAvailable(Catch2)
+    FetchContent_Declare(
+      Catch2
+      GIT_REPOSITORY https://github.com/catchorg/Catch2.git
+      GIT_TAG        v3.0.1 # or a later release
+    )
+
+    FetchContent_MakeAvailable(Catch2)
+endif()
 
 file(GLOB_RECURSE src_files "*.cpp")