Build: Switch to CMake :^)

Closes https://github.com/SerenityOS/serenity/issues/2080

Libraries/LibCore/CMakeLists.txt

@@ -0,0 +1,32 @@
+set(SOURCES
+    ArgsParser.cpp
+    ConfigFile.cpp
+    DateTime.cpp
+    DirIterator.cpp
+    ElapsedTimer.cpp
+    Event.cpp
+    EventLoop.cpp
+    File.cpp
+    Gzip.cpp
+    IODevice.cpp
+    LocalServer.cpp
+    LocalSocket.cpp
+    MimeData.cpp
+    NetworkJob.cpp
+    NetworkResponse.cpp
+    Notifier.cpp
+    Object.cpp
+    ProcessStatisticsReader.cpp
+    puff.c
+    SocketAddress.cpp
+    Socket.cpp
+    StandardPaths.cpp
+    TCPServer.cpp
+    TCPSocket.cpp
+    Timer.cpp
+    UDPServer.cpp
+    UDPSocket.cpp
+)
+
+serenity_lib(LibCore core)
+target_link_libraries(LibCore LibC)