Added missing find_package()

Author: cschreib

libjsonexpr/CMakeLists.txt

@@ -9,13 +9,18 @@ if (NOT JSONEXPR_USE_SYSTEM_JSON)
     FetchContent_Declare(json
                          URL https://github.com/nlohmann/json/archive/refs/tags/v3.11.3.zip)
     FetchContent_MakeAvailable(json)
+else()
+    find_package(nlohmann_json REQUIRED)
 endif()
+
 if (NOT JSONEXPR_USE_STD_EXPECTED AND NOT JSONEXPR_USE_SYSTEM_EXPECTED)
     set(EXPECTED_BUILD_TESTS OFF)
     set(EXPECTED_BUILD_PACKAGE_DEB OFF)
     FetchContent_Declare(expected
                          URL https://github.com/TartanLlama/expected/archive/refs/tags/v1.1.0.zip)
     FetchContent_MakeAvailable(expected)
+else()
+    find_package(tl-expected REQUIRED)
 endif()
 
 if (DEFINED BUILD_SHARED_LIBS)