Fix conanfile.py/CMakeLists.txt for C consumers

The new configuration should make C consumers link to "stdc++" by
default, which should fix building with static libs for C programs.

CMakeLists.txt

@@ -1,7 +1,7 @@
 cmake_minimum_required(VERSION 3.7)
 project(UDPC)
 
-set(UDPC_VERSION 1.1)
+set(UDPC_VERSION 1.2)
 set(UDPC_SOVERSION 1)
 
 set(UDPC_SOURCES
@@ -42,6 +42,12 @@ find_package(libsodium REQUIRED)
 target_compile_definitions(UDPC PUBLIC UDPC_LIBSODIUM_ENABLED)
 target_link_libraries(UDPC PUBLIC libsodium::libsodium)
 
+# Enforce linking with libstdc++ even with C targets.
+# Doesn't affect conan, so conanfile.py was also modified for this.
+set_target_properties(UDPC PROPERTIES
+    INTERFACE_LINK_LIBRARIES "stdc++"
+)
+
 if(CMAKE_BUILD_TYPE MATCHES "Debug")
     set(UDPC_UnitTest_SOURCES
         src/CXX11_shared_spin_lock.cpp

conan_usage_example/CMakeLists.txt

@@ -22,4 +22,4 @@ find_package(udpc CONFIG REQUIRED)
 add_executable(UDPC_NetworkTest
     ${UDPC_NetworkTest_SOURCES}
 )
-target_link_libraries(UDPC_NetworkTest udpc::udpc stdc++)
+target_link_libraries(UDPC_NetworkTest PUBLIC udpc::udpc)

conan_usage_example/conanfile.txt

@@ -1,5 +1,5 @@
 [requires]
-udpc/1.1
+udpc/1.2
 
 [generators]
 CMakeDeps

conanfile.py

@@ -5,7 +5,7 @@ import os
 
 class udpcRecipe(ConanFile):
     name = "udpc"
-    version = "1.1"
+    version = "1.2"
     package_type = "library"
 
     # Optional metadata
@@ -54,4 +54,4 @@ class udpcRecipe(ConanFile):
 
     def package_info(self):
         self.cpp_info.libs = ["UDPC"]
-
+        self.cpp_info.system_libs = ["stdc++"]