cmake: disable 64BIT flag by default only for 32-bit archs and 64-bit windows and linux

CMakeLists.txt

@@ -44,7 +44,17 @@ option(USE_VOICEMGR "Enable VOICE MANAGER." OFF)
 option(BUILD_CLIENT "Build client dll" ON)
 option(BUILD_SERVER "Build server dll" ON)
 option(GOLDSOURCE_SUPPORT "Build goldsource compatible client library" OFF)
-option(64BIT "Disable auto -m32 appending to compiler flags" OFF)
+
+if (CMAKE_SIZEOF_VOID_P EQUAL 4 OR
+	(WIN32 OR ${CMAKE_SYSTEM_NAME} STREQUAL "Linux")
+	AND (CMAKE_SYSTEM_PROCESSOR STREQUAL "x64"
+	OR CMAKE_SYSTEM_PROCESSOR STREQUAL "x86_64"
+	OR CMAKE_SYSTEM_PROCESSOR STREQUAL "amd64"))
+	option(64BIT "Disable auto -m32 appending to compiler flags" OFF)
+else()
+	option(64BIT "Disable auto -m32 appending to compiler flags" ON)
+endif()
+
 set(GAMEDIR "valve" CACHE STRING "Gamedir path")
 set(SERVER_INSTALL_DIR "dlls" CACHE STRING "Where put server dll")
 set(CLIENT_INSTALL_DIR "cl_dlls" CACHE STRING "Where put client dll")