CMakeLists: Remove iconv from the LIBS variable

Adjusts Common to use the ICONV_LIBRARIES variable directly and doesn't
append it to the LIBS variable.

After this, there's only one remaining usage where libraries are added
to the LIBS variable, after which it can be removed once the rest of
the targets are migrated off add_dolphin_library

CMakeLists.txt

@@ -706,7 +706,6 @@ else()
   add_subdirectory(Externals/libiconv-1.14)
   set(ICONV_LIBRARIES iconv)
 endif()
-list(APPEND LIBS ${ICONV_LIBRARIES})
 
 if(NOT ANDROID)
   find_package(HIDAPI)

Source/Core/Common/CMakeLists.txt

@@ -44,12 +44,16 @@ add_library(common
   x64Emitter.cpp
 )
 
-target_link_libraries(common PUBLIC
+target_link_libraries(common
+PUBLIC
   ${CMAKE_THREAD_LIBS_INIT}
   ${CURL_LIBRARIES}
   enet
   ${MBEDTLS_LIBRARIES}
   ${VTUNE_LIBRARIES}
+
+PRIVATE
+  ${ICONV_LIBRARIES}
 )
 
 if (APPLE)
@@ -65,7 +69,6 @@ if(ANDROID)
   target_sources(common PRIVATE
     Logging/ConsoleListenerDroid.cpp
   )
-  target_link_libraries(common PRIVATE iconv)
 elseif(WIN32)
   target_sources(common PRIVATE
     Logging/ConsoleListenerWin.cpp