feat(macos): build a signed .app bundle in a .dmg (#4759)

cmake/targets/macos.cmake

@@ -1,4 +1,26 @@
 # macos specific target definitions
-target_link_options(sunshine PRIVATE LINKER:-sectcreate,__TEXT,__info_plist,${APPLE_PLIST_FILE})
+
+if (SUNSHINE_BUILD_HOMEBREW)
+    target_link_options(sunshine PRIVATE LINKER:-sectcreate,__TEXT,__info_plist,${APPLE_PLIST_FILE})
+else()
+    # .app build
+    set_target_properties(sunshine PROPERTIES
+            OUTPUT_NAME "${CMAKE_PROJECT_NAME}"
+            MACOSX_BUNDLE_BUNDLE_NAME "${CMAKE_PROJECT_NAME}"
+            MACOSX_BUNDLE_GUI_IDENTIFIER "${PROJECT_FQDN}"
+            MACOSX_BUNDLE_INFO_PLIST "${APPLE_PLIST_FILE}"
+            MACOSX_BUNDLE_ICON_FILE "sunshine.icns"
+            MACOSX_BUNDLE_SHORT_VERSION_STRING "${PROJECT_VERSION}"
+            MACOSX_BUNDLE_BUNDLE_VERSION "${PROJECT_VERSION}")
+
+    # Populate bundle resources in the build tree for local runs.
+    set(_bundle_resources_dir "$<TARGET_FILE_DIR:sunshine>/../Resources")
+    add_custom_command(TARGET sunshine POST_BUILD
+            COMMENT "Copying bundle resources to build tree"
+            COMMAND "${CMAKE_COMMAND}" -E make_directory "${_bundle_resources_dir}"
+            COMMAND "${CMAKE_COMMAND}" -E copy_directory "${CMAKE_BINARY_DIR}/assets" "${_bundle_resources_dir}/assets"
+            VERBATIM)
+endif()
+
 # Tell linker to dynamically load these symbols at runtime, in case they're unavailable:
 target_link_options(sunshine PRIVATE -Wl,-U,_CGPreflightScreenCaptureAccess -Wl,-U,_CGRequestScreenCaptureAccess)