add detailed note regarding dawn modifications to fix linker errors on mac

Author: austinvhuang

third_party/lib/README.md

@@ -15,6 +15,70 @@ cmake -DBUILD_SHARED_LIBS=ON -DDAWN_BUILD_MONOLITHIC_LIBRARY=ON -DCMAKE_BUILD_TY
 ```
 Library artifact is at `src/dawn/native/libwebgpu_dawn.dylib` (7.4 MB)
 
+Note that for OSX builds, needed to make modifications to the `CMakeLists.txt` file to get the build to work. Specifically, needed to add the following `FORCE_OBJECT` flags to dawn_glfw, dawn_wgpu_utils, and dawn_test_utils. Otherwise we get linker errors for missing symbols when building the shared library. This issue does not appear to be present on Linux builds.
+
+```
+(base) austinhuang@Austins-MacBook-Pro dawn % git diff 556f960f44690b3b808c779c08b44d48d4292925 5a00ab1fbc22d6ebbab39  
+diff --git a/src/dawn/glfw/CMakeLists.txt b/src/dawn/glfw/CMakeLists.txt
+index dc3f3ade03..d6d8d0ef4f 100644
+--- a/src/dawn/glfw/CMakeLists.txt
++++ b/src/dawn/glfw/CMakeLists.txt
+@@ -40,6 +40,7 @@ endif ()
+ 
+ dawn_add_library(
+   dawn_glfw
++  FORCE_OBJECT
+   UTILITY_TARGET dawn_internal_config
+   HEADERS
+     "${headers}"
+@@ -56,5 +57,5 @@ target_compile_definitions(dawn_glfw PRIVATE "WGPU_GLFW_IMPLEMENTATION")
+ if(BUILD_SHARED_LIBS)
+     target_compile_definitions(dawn_glfw PUBLIC "WGPU_GLFW_SHARED_LIBRARY")
+ endif()
+-
++# target_link_libraries(dawn_glfw PUBLIC webgpu_dawn)
+ add_library(webgpu_glfw ALIAS dawn_glfw)
+diff --git a/src/dawn/utils/CMakeLists.txt b/src/dawn/utils/CMakeLists.txt
+index 5eb7120d99..3b00664829 100644
+--- a/src/dawn/utils/CMakeLists.txt
++++ b/src/dawn/utils/CMakeLists.txt
+@@ -36,6 +36,7 @@ endif()
+ 
+ dawn_add_library(
+   dawn_wgpu_utils
++  FORCE_OBJECT
+   ENABLE_EMSCRIPTEN
+   UTILITY_TARGET dawn_internal_config
+   PRIVATE_HEADERS
+@@ -55,6 +56,8 @@ dawn_add_library(
+     ${private_wgpu_depends}
+ )
+ 
++# target_link_libraries(dawn_wgpu_utils PUBLIC webgpu_dawn)
++
+ # Needed by WGPUHelpers
+ target_compile_definitions(dawn_wgpu_utils
+   PUBLIC
+@@ -66,6 +69,7 @@ target_compile_definitions(dawn_wgpu_utils
+ ###############################################################################
+ dawn_add_library(
+   dawn_test_utils
++  FORCE_OBJECT
+   UTILITY_TARGET dawn_internal_config
+   PRIVATE_HEADERS
+     "BinarySemaphore.h"
+@@ -84,6 +88,9 @@ dawn_add_library(
+     dawn::partition_alloc
+ )
+ 
++# target_link_libraries(dawn_test_utils PUBLIC webgpu_dawn dawn_wgpu_utils dawn_proc)
++
++
+ ###############################################################################
+ # Dawn system utilities
+ #   - Used in tests and samples
+ ```
+
 # Release 0.1.0
 
 https://github.com/jspanchu/webgpu-dawn-binaries