Turns out cstdint is c++11, so enabled c++11 on sourcesdk project.

external/sourcesdk/include/sourcesdk/valve_support.h

@@ -7,16 +7,16 @@
 #include <string.h>
 #include "vector.h"
 
-typedef std::uint64_t uint64;
-typedef std::uint32_t uint32;
-typedef std::uint16_t uint16;
-typedef std::uint8_t uint8;
-typedef std::int64_t int64;
-typedef std::int32_t int32;
-typedef std::int16_t int16;
-typedef std::int8_t int8;
-typedef unsigned int uint;
-typedef char byte;
+using uint64 = std::uint64_t;
+using uint32 = std::uint32_t;
+using uint16 = std::uint16_t;
+using uint8 = std::uint8_t;
+using int64 = std::int64_t;
+using int32 = std::int32_t;
+using int16 = std::int16_t;
+using int8 = std::int8_t;
+using uint = unsigned int;
+using byte = char;
 
 #if defined(_M_IX86)
 #define __i386__ 1

premake/premake5.lua

@@ -20,7 +20,6 @@ solution "demboyz"
         kind "ConsoleApp"
         language "C++"
         configuration "gmake"
-            -- Enables C++11 support.
             buildoptions { "-std=c++11" }
         configuration {}
         files

premake/sourcesdk.lua

@@ -7,7 +7,9 @@ group "external"
         kind "StaticLib"
         language "C++"
         location (_ACTION .. "/" .. project().name)
-
+        configuration "gmake"
+            buildoptions { "-std=c++11" }
+        configuration {}
         includedirs
         {
             base_dir .. "include/",