[spirv-writer] Add switch support

This CL adds switch support to the SPIR-V writer.

Bug: tint:5
Change-Id: I8a6ad40cb2d344c87abdf842194b60afb1b4c96e
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/22165
Reviewed-by: David Neto <dneto@google.com>
diff --git a/BUILD.gn b/BUILD.gn
index 73f3454..2adbf02 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -692,6 +692,7 @@
     "src/writer/spirv/builder_literal_test.cc",
     "src/writer/spirv/builder_loop_test.cc",
     "src/writer/spirv/builder_return_test.cc",
+    "src/writer/spirv/builder_switch_test.cc",
     "src/writer/spirv/builder_test.cc",
     "src/writer/spirv/builder_type_test.cc",
     "src/writer/spirv/builder_unary_op_expression_test.cc",