move to new build system

cmake/os.cmake

@@ -0,0 +1,15 @@
+if(MSVC)
+  message(FATAL_ERROR "MSVC will not be supported")
+endif()
+
+if(UNIX AND APPLE)
+  message(FATAL_ERROR "Apple is not currently supported")
+endif()
+
+if(${CMAKE_SYSTEM_NAME} MATCHES "FreeBSD")
+  message(FATAL_ERROR "FreeBSD is not currently supported")
+endif()
+
+if(PROJECT_REQUIRE_ALPINE AND NOT PROJECT_IS_ALPINE AND PROJECT_IS_MINGW AND PROJECT_IS_MINGW_UNIX)
+  message(FATAL_ERROR "Project requires Alpine Linux to build")
+endif()