Use system jansson explicitly if needed

Signed-off-by: Osyotr <Osyotr@users.noreply.github.com>

3party/CMakeLists.txt

@@ -32,6 +32,7 @@ if (NOT WITH_SYSTEM_PROVIDED_3PARTY)
   set(JANSSON_WITHOUT_TESTS ON)
   add_subdirectory(jansson/jansson/)
   target_include_directories(jansson INTERFACE "${PROJECT_BINARY_DIR}/3party/jansson/jansson/include")
+  add_library(jansson::jansson ALIAS jansson)
 
   # Add gflags library.
   add_subdirectory(gflags)

CMakeLists.txt

@@ -324,6 +324,7 @@ if (WITH_SYSTEM_PROVIDED_3PARTY)
   find_package(gflags REQUIRED)
 
   find_package(expat CONFIG REQUIRED)
+  find_package(jansson CONFIG REQUIRED)
   find_package(utf8cpp REQUIRED)
 endif()
 

cppjansson/CMakeLists.txt

@@ -9,5 +9,5 @@ omim_add_library(${PROJECT_NAME} ${SRC})
 target_link_libraries(${PROJECT_NAME}
   PUBLIC
     base
-    jansson
+    jansson::jansson
 )