chore(build): add cmake config

CMakeLists.txt

@@ -0,0 +1,21 @@
+cmake_minimum_required(VERSION 3.1)
+
+if (${CMAKE_SOURCE_DIR} STREQUAL ${CMAKE_BINARY_DIR})
+    message(FATAL_ERROR
+        "In-source builds not allowed.
+        Please make a new directory (called a build directory) and run CMake from there.
+        You may need to remove CMakeCache.txt."
+    )
+endif()
+
+if(TARGET system)
+    # Guard for use as transitive dependency
+    return()
+endif()
+
+# Project
+project(system)
+
+set(CMAKE_CXX_STANDARD 11)
+
+add_subdirectory(system)

system/CMakeLists.txt

@@ -0,0 +1,6 @@
+add_library(system INTERFACE)
+
+target_include_directories(system
+    INTERFACE
+        ${PROJECT_SOURCE_DIR}
+)