Use the correct V8_HOST_ARCH macro, it is IA32 and not X86.

src/platform-linux.cc

Index: src/platform-linux.cc
diff --git a/src/platform-linux.cc b/src/platform-linux.cc
index 418113b52eb33cef42ab374cdcfdd72a4695696c..026d251f5c339c5e5c8b2a29cc2403597d43e7d4 100644
--- a/src/platform-linux.cc
+++ b/src/platform-linux.cc
@@ -600,7 +600,7 @@ static void ProfilerSignalHandler(int signal, siginfo_t* info, void* context) {
     // Extracting the sample from the context is extremely machine dependent.
     ucontext_t* ucontext = reinterpret_cast<ucontext_t*>(context);
     mcontext_t& mcontext = ucontext->uc_mcontext;
-#if V8_HOST_ARCH_X86
+#if V8_HOST_ARCH_IA32
     sample.pc = mcontext.gregs[REG_EIP];
     sample.sp = mcontext.gregs[REG_ESP];
     sample.fp = mcontext.gregs[REG_EBP];