Add support for SPIRV writing to BUILD.gn

BUG=tint:48

Change-Id: I6b92bb372b783ad4498fdc4817d0893851b0bb90
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/19680
Reviewed-by: dan sinclair <dsinclair@google.com>

src/writer/spirv/builder.cc

@@ -223,7 +223,7 @@ uint32_t Builder::GenerateExpressionAndLoad(ast::Expression* expr) {
     error_ = "missing generated ID for variable";
     return 0;
   }
-  auto var = spirv_id_to_variable_[id];
+  auto* var = spirv_id_to_variable_[id];
   if (var->is_const()) {
     return id;
   }
@@ -457,7 +457,7 @@ uint32_t Builder::GenerateConstructorExpression(
     return GenerateLiteralIfNeeded(expr->AsScalarConstructor()->literal());
   }
   if (expr->IsTypeConstructor()) {
-    auto init = expr->AsTypeConstructor();
+    auto* init = expr->AsTypeConstructor();
     auto type_id = GenerateTypeIfNeeded(init->type());
     if (type_id == 0) {
       return 0;
@@ -568,7 +568,7 @@ uint32_t Builder::GenerateBinaryExpression(ast::BinaryExpression* expr) {
 
   // Handle int and float and the vectors of those types. Other types
   // should have been rejected by validation.
-  auto lhs_type = expr->lhs()->result_type();
+  auto* lhs_type = expr->lhs()->result_type();
   bool lhs_is_float_or_vec =
       lhs_type->IsF32() ||
       (lhs_type->IsVector() && lhs_type->AsVector()->type()->IsF32());
@@ -888,7 +888,7 @@ bool Builder::GeneratePointerType(ast::type::PointerType* ptr,
 bool Builder::GenerateStructType(ast::type::StructType* struct_type,
                                  const Operand& result) {
   auto struct_id = result.to_i();
-  auto impl = struct_type->impl();
+  auto* impl = struct_type->impl();
 
   if (!struct_type->name().empty()) {
     push_debug(spv::Op::OpName,

src/writer/spirv/function.cc

@@ -27,6 +27,8 @@ Function::Function(const Instruction& declaration,
                    const std::vector<Instruction>& params)
     : declaration_(declaration), label_op_(label_op), params_(params) {}
 
+Function::Function(const Function& other) = default;
+
 Function::~Function() = default;
 
 void Function::iterate(std::function<void(const Instruction&)> cb) const {

src/writer/spirv/function.h

@@ -42,7 +42,7 @@ class Function {
            const std::vector<Instruction>& params);
   /// Copy constructor
   /// @param other the function to copy
-  Function(const Function& other) = default;
+  Function(const Function& other);
   ~Function();
 
   /// Iterates over the function call the cb on each instruction

src/writer/spirv/instruction.cc

@@ -23,6 +23,8 @@ namespace spirv {
 Instruction::Instruction(spv::Op op, std::vector<Operand> operands)
     : op_(op), operands_(std::move(operands)) {}
 
+Instruction::Instruction(const Instruction&) = default;
+
 Instruction::~Instruction() = default;
 
 uint32_t Instruction::word_length() const {

src/writer/spirv/instruction.h

@@ -32,7 +32,7 @@ class Instruction {
   /// @param operands the operand values for the instruction
   Instruction(spv::Op op, std::vector<Operand> operands);
   /// Copy Constructor
-  Instruction(const Instruction&) = default;
+  Instruction(const Instruction&);
   ~Instruction();
 
   /// @returns the instructions op