[jumbo] fix B macro/symbol clashes in arm64 builds

assembler-arm64.h and assembler-arm64-inl.h have a B() function
which conflicts with the B macro in bytecode-utils.h.

Headers that leak macros can be annoying to deal with, in this case
we can't simply undef B at the end of source files that include
bytecode-utils.h because the second source file that includes
bytecode-utils.h won't see the B macro.  Let's just move this macro
into the two unittest files that include this header.

Bug: chromium:746958
Change-Id: I588b73fe81615f882a0e010c92ba187d3bc2bf25
Reviewed-on: https://chromium-review.googlesource.com/758779
Commit-Queue: Mostyn Bramley-Moore <mostynb@vewd.com>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49258}

test/unittests/interpreter/bytecode-array-writer-unittest.cc

@@ -24,6 +24,7 @@ namespace internal {
 namespace interpreter {
 namespace bytecode_array_writer_unittest {
 
+#define B(Name) static_cast<uint8_t>(Bytecode::k##Name)
 #define R(i) static_cast<uint32_t>(Register(i).ToOperand())
 
 class BytecodeArrayWriterUnittest : public TestWithIsolateAndZone {
@@ -364,6 +365,7 @@ TEST_F(BytecodeArrayWriterUnittest, DeadcodeElimination) {
   CHECK(source_iterator.done());
 }
 
+#undef B
 #undef R
 
 }  // namespace bytecode_array_writer_unittest

test/unittests/interpreter/bytecode-decoder-unittest.cc

@@ -16,6 +16,8 @@ namespace v8 {
 namespace internal {
 namespace interpreter {
 
+#define B(Name) static_cast<uint8_t>(Bytecode::k##Name)
+
 TEST(BytecodeDecoder, DecodeBytecodeAndOperands) {
   struct BytecodesAndResult {
     const uint8_t bytecode[32];
@@ -95,6 +97,8 @@ TEST(BytecodeDecoder, DecodeBytecodeAndOperands) {
   }
 }
 
+#undef B
+
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8

test/unittests/interpreter/bytecode-utils.h

@@ -27,7 +27,6 @@
 #endif
 
 #define U8(i) static_cast<uint8_t>(i)
-#define B(Name) static_cast<uint8_t>(Bytecode::k##Name)
 #define REG_OPERAND(i) \
   (InterpreterFrameConstants::kRegisterFileFromFp / kPointerSize - (i))
 #define R8(i) static_cast<uint8_t>(REG_OPERAND(i))