[metal-writer] Emit functions

This Cl adds the code to emit functions from the metal writer. Note,
this does not handle entry points yet.

Bug: tint:8
Change-Id: Ie665771169261f6839de5eb1b66dc511bf47616a
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/23704
Reviewed-by: David Neto <dneto@google.com>
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 317b523..ba497fc 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -493,6 +493,7 @@
 
 if(${TINT_BUILD_MSL_WRITER})
   list(APPEND TINT_TEST_SRCS
+    writer/msl/generator_impl_function_test.cc
     writer/msl/generator_impl_identifier_test.cc
     writer/msl/generator_impl_return_test.cc
     writer/msl/generator_impl_test.cc