Reimplement InsertPointGuard to avoid LLVM ABI incompatibility.

In general, the NDEBUG flag should match cpp-ethereum and LLVM builds. But this is hard to satisfy as we usually have one system-wide build of LLVM and different builds of cpp-ethereum. This ABI incompatibility hit OSX only in release builds as LLVM is built by homebrew with assertions by default.

evmjit/libevmjit/CompilerHelper.h

@@ -49,7 +49,15 @@ private:
 	RuntimeManager& m_runtimeManager;
 };
 
-using InsertPointGuard = llvm::IRBuilderBase::InsertPointGuard;
+struct InsertPointGuard
+{
+	explicit InsertPointGuard(llvm::IRBuilderBase& _builder): m_builder(_builder), m_insertPoint(_builder.saveIP()) {}
+	~InsertPointGuard() { m_builder.restoreIP(m_insertPoint); }
+
+private:
+	llvm::IRBuilderBase& m_builder;
+	decltype(m_builder.saveIP()) m_insertPoint;
+};
 
 }
 }