Upstream support for OpenBSD. (#414)

CMakeLists.txt

@@ -62,8 +62,10 @@ endif()
 
 list(APPEND CMAKE_MODULE_PATH "${DevilutionX_SOURCE_DIR}/CMake")
 
-if(${CMAKE_SYSTEM_NAME} STREQUAL FreeBSD)
+if(${CMAKE_SYSTEM_NAME} STREQUAL FreeBSD OR ${CMAKE_SYSTEM_NAME} STREQUAL OpenBSD)
   set(ASAN OFF)
+  set(UBSAN OFF)
+  add_definitions(-D_BSD_SOURCE)
   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -DO_LARGEFILE=0 -Dstat64=stat -Dlstat64=lstat -Dlseek64=lseek -Doff64_t=off_t -Dfstat64=fstat -Dftruncate64=ftruncate")
 endif()
 

SourceS/miniwin.h

@@ -3,7 +3,7 @@
 #include <ctype.h>
 #include <math.h>
 // work around https://reviews.llvm.org/D51265
-#if defined(__APPLE__) || defined(__FreeBSD__)
+#if defined(__APPLE__) || defined(__FreeBSD__) || defined(__OpenBSD__)
 #include "macos_stdarg.h"
 #else
 #include <stdarg.h>