CMake: Enable -Wl,--no-undefined on ELF platforms

This is mostly a development helper, to move all undefined symbols
in shared libraries to link time rather than load time.

At the same time, set --no-allow-shlib-undefined and -z,defs to
further enforce the rule.

Meta/CMake/collections.cmake

@@ -15,6 +15,11 @@ set(BUILD_TESTING_SAVE ${BUILD_TESTING})
 set(BUILD_TESTING OFF)
 set(BUILD_EXAMPLES OFF)
 
+# FIXME: https://github.com/apple/swift-collections/issues/440
+set(BUILD_SHARED_LIBS_SAVE ${BUILD_SHARED_LIBS})
+set(BUILD_SHARED_LIBS OFF)
+
 FetchContent_MakeAvailable(SwiftCollections)
 
+set(BUILD_SHARED_LIBS ${BUILD_SHARED_LIBS_SAVE})
 set(BUILD_TESTING ${BUILD_TESTING_SAVE})

Meta/CMake/lagom_compile_options.cmake

@@ -54,6 +54,13 @@ if (NOT WIN32)
     endif()
 endif()
 
+if (NOT WIN32 AND NOT APPLE AND NOT ENABLE_FUZZERS)
+    # NOTE: Assume ELF
+    add_link_options(LINKER:-z,defs)
+    add_link_options(LINKER:--no-undefined)
+    add_link_options(LINKER:--no-allow-shlib-undefined)
+endif()
+
 if (ENABLE_LAGOM_COVERAGE_COLLECTION)
     if (CMAKE_CXX_COMPILER_ID MATCHES "Clang$" AND NOT ENABLE_FUZZERS)
         add_cxx_compile_options(-fprofile-instr-generate -fcoverage-mapping)

Meta/Lagom/ClangPlugins/CMakeLists.txt

@@ -16,6 +16,11 @@ function(clang_plugin target_name)
     set_property(GLOBAL APPEND PROPERTY CLANG_PLUGINS_COMPILE_OPTIONS_FOR_TESTS -fplugin=${CMAKE_BINARY_DIR}/${CMAKE_INSTALL_LIBDIR}/lib${target_name}.so)
 
     add_lagom_library_install_rules(${target_name})
+
+    if (NOT WIN32 AND NOT APPLE)
+        target_link_options(${target_name} PRIVATE LINKER:-z,undefs)
+        target_link_options(${target_name} PRIVATE LINKER:--allow-shlib-undefined)
+    endif()
 endfunction()
 
 function(depend_on_clang_plugin target_name plugin_name)