[spirv-writer] Add identifier expressions

This Cl adds the code to convert an identifer expression into an ID.

Bug: tint:5
Change-Id: Id6cb08404f091fd4d89c3f7f9292c9de2eb4fa65
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/18601
Reviewed-by: David Neto <dneto@google.com>
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 8ad3e2c..6f09163 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -420,6 +420,7 @@
     writer/spirv/builder_function_test.cc
     writer/spirv/builder_function_variable_test.cc
     writer/spirv/builder_global_variable_test.cc
+    writer/spirv/builder_ident_expression_test.cc
     writer/spirv/builder_literal_test.cc
     writer/spirv/builder_return_test.cc
     writer/spirv/builder_test.cc