[cmake] Fix build if '-Wl,--no-undefined' is specified in CMAKE_SHARE…

…D_LINKER_FLAGS.

Also add '-Wl,--no-undefined' to the linker options of the base library.

CMakeLists.txt

@@ -48,6 +48,9 @@ cmake_dependent_option(BUILD_EXAMPLES
   "whether to build the examples (requires BUILD_LIBRARIES to be ON)" OFF
   "BUILD_LIBRARIES" OFF)
 
+# Do not report undefined references in libraries, since the protocol libraries cannot be used on their own.
+string(REPLACE "-Wl,--no-undefined" "" CMAKE_SHARED_LINKER_FLAGS ${CMAKE_SHARED_LINKER_FLAGS})
+
 # variables for .pc.in files
 set(prefix "${CMAKE_INSTALL_PREFIX}")
 set(bindir "${CMAKE_INSTALL_FULL_BINDIR}")
@@ -154,6 +157,8 @@ if(BUILD_LIBRARIES)
   define_library(wayland-client++ "${WAYLAND_CLIENT_CFLAGS}" "${WAYLAND_CLIENT_LIBRARIES}"
     "include/wayland-client.hpp;include/wayland-util.hpp;${CMAKE_CURRENT_BINARY_DIR}/wayland-client-protocol.hpp;${CMAKE_CURRENT_BINARY_DIR}/wayland-version.hpp"
     src/wayland-client.cpp src/wayland-util.cpp wayland-client-protocol.cpp wayland-client-protocol.hpp)
+  # Report undefined references only for the base library.
+  target_link_options(wayland-client++ PRIVATE "-Wl,--no-undefined")
   define_library(wayland-client-extra++ "${WAYLAND_CLIENT_CFLAGS}" "${WAYLAND_CLIENT_LIBRARIES}"
     "${CMAKE_CURRENT_BINARY_DIR}/wayland-client-protocol-extra.hpp"
     wayland-client-protocol-extra.cpp wayland-client-protocol-extra.hpp wayland-client-protocol.hpp)