Add a CMake compile time option for building a 64bit binary.

By default the cmake build will still cross compile a 32bit binary and spout a message about it if not enabled.
This doesn't fix the 64bit build issues, just makes it easier for someone to test 64bit builds in the future.
Look towards a bright future instead of a dark and gloomy past

CMakeLists.txt

@@ -1,3 +1,6 @@
+# CMake options
+option(64BIT_BUILD "Enable a x86_64 build instead of cross compiling (developer option)" OFF)
+
 # Project Name
 project(Pcsx2)
 
@@ -40,6 +43,16 @@ if(POLICY CMP0022)
     cmake_policy(SET CMP0022 OLD)
 endif()
 
+# Architecture bitness detection
+if(CMAKE_SIZEOF_VOID_P EQUAL 8)
+	set(_ARCH_64 1)
+	add_definitions(-D_ARCH_64=1)
+else()
+	set(_ARCH_32 1)
+	add_definitions(-D_ARCH_32=1)
+endif()
+
+
 # Variable to check that people use the good file
 set(TOP_CMAKE_WAS_SOURCED TRUE)
 
@@ -47,17 +60,18 @@ set(TOP_CMAKE_WAS_SOURCED TRUE)
 # It would avoid compilation failure later.
 # Note: disable the failure in package mode
 if(NOT PACKAGE_MODE)
-    if(CMAKE_SIZEOF_VOID_P MATCHES "8")
+    if(_ARCH_64 AND !64BIT_BUILD)
         message(WARNING "
         PCSX2 does not support a 64-bits environment and has no plan to support a 64-bits architecture in the future.
         It would need a complete rewrite of the core emulator and a lot of time.
 
         You can still run a 32-bits binary if you install all 32-bits libraries (runtime and dev).")
-    endif(CMAKE_SIZEOF_VOID_P MATCHES "8")
+    endif()
 endif(NOT PACKAGE_MODE)
 
-# 64 bits specific configuration
-if(CMAKE_SIZEOF_VOID_P MATCHES "8")
+# 64 bits cross-compile specific configuration
+if(_ARCH_64 AND !64BIT_BUILD)
+    message("Compiling 32bit build on 64bit architecture")
     # Do not search library in /usr/lib64
     SET_PROPERTY(GLOBAL PROPERTY FIND_LIBRARY_USE_LIB64_PATHS OFF)
     # Probably useless but it will not harm
@@ -67,13 +81,11 @@ if(CMAKE_SIZEOF_VOID_P MATCHES "8")
     if(EXISTS "/usr/lib32")
         set(CMAKE_LIBRARY_ARCHITECTURE "../lib32")
     endif()
-endif(CMAKE_SIZEOF_VOID_P MATCHES "8")
-
     # Debian/ubuntu drop /usr/lib32 and move /usr/lib to /usr/lib/i386-linux-gnu
     if(EXISTS "/usr/lib/i386-linux-gnu")
         set(CMAKE_LIBRARY_ARCHITECTURE "i386-linux-gnu")
     endif()
-
+endif()
 
 # * -fPIC option was removed for multiple reasons.
 #     - Code only supports the x86 architecture.

cmake/BuildParameters.cmake

@@ -98,7 +98,11 @@ set(CMAKE_SHARED_LIBRARY_CXX_FLAGS "")
 # -Wno-unused-function: warn for function not used in release build
 set(DEFAULT_WARNINGS "-Wno-attributes -Wstrict-aliasing -Wno-missing-field-initializers -Wno-unused-function")
 set(HARDEING_OPT "-D_FORTIFY_SOURCE=2  -Wformat -Wformat-security")
+if(_ARCH_64 AND !64BIT_BUILD)
 	set(DEFAULT_GCC_FLAG "-m32 -msse -msse2 -march=i686 -pthread ${DEFAULT_WARNINGS} ${HARDEING_OPT}")
+else()
+	set(DEFAULT_GCC_FLAG "-msse -msse2 -pthread ${DEFAULT_WARNINGS} ${HARDEING_OPT}")
+endif()
 if(CMAKE_BUILD_TYPE MATCHES "Debug|Devel")
     set(DEFAULT_GCC_FLAG "-g ${DEFAULT_GCC_FLAG}")
 endif()

cmake/SearchForStuff.cmake

@@ -143,7 +143,7 @@ if(wxWidgets_FOUND)
     if(Linux)
         # Force the use of 32 bit library configuration on
         # 64 bits machine with 32 bits library in /usr/lib32
-        if(CMAKE_SIZEOF_VOID_P MATCHES "8")
+        if(_ARCH_64 AND !64BIT_BUILD)
             ## There is no guarantee that wx-config is a link to a 32 bits library. So you need to force the destinity
             # Library can go into 3 path major paths (+ multiarch but you will see that later when implementation is done)
             # 1/ /usr/lib32 (32 bits only)