Export OpenSSL dependency

CMakeLists.txt

@@ -120,8 +120,10 @@ target_include_directories(${module_name}
         ${CMAKE_CURRENT_SOURCE_DIR}/src
 )
 
+set(AIDGE_REQUIRES_OPENSSL FALSE)
 if(OpenSSL_FOUND)
     target_link_libraries(${module_name} PRIVATE OpenSSL::SSL OpenSSL::Crypto)
+    set(AIDGE_REQUIRES_OPENSSL TRUE)
 endif()
 
 target_compile_features(${module_name} PRIVATE cxx_std_14)

aidge_backend_cpu-config.cmake.in

@@ -2,6 +2,10 @@
 
 include(CMakeFindDependencyMacro)
 find_dependency(aidge_core)
+set(AIDGE_REQUIRES_OPENSSL @AIDGE_REQUIRES_OPENSSL@)
+if (AIDGE_REQUIRES_OPENSSL)
+    find_dependency(OpenSSL)
+endif()
 
 include(CMakeFindDependencyMacro)