CMakeLists.txt: Add ARM based Linux PLATFORM_ARCH

* Don't assume all Linux systems are strictly x86.
* Add values when Linux is used on an ARM device

Signed-off-by: Franklin S Cooper Jr <fcooper27@gmail.com>
CMakeLists.txt: Add BB as a supported board

* Some of the configuration needs to be tweaked when building for a Beaglebone
  and Beaglebone Black.
* Unlike the Raspberry PI there aren't any files to check against to determine
  at build time if this is being built for the Raspberry PI. Therefore, create
  a variable that the user has to pass in (-DBB:BOOL=ON) that will tell CMAKE
  to build PPSSPPSDL for the BB/BBB.
* This will also make it alot easier for users to cross compile for this device

Signed-off-by: Franklin S Cooper Jr <fcooper27@gmail.com>
MemArena.cpp: Fix Bus Error when running on Beaglebone/Beaglebone Black

* Similar to commit 178891b57608a8df1541b3f7fc6ee83ad1b50989 when running the
  emulator a "Bus Error" would be given andn will cause a seg fault immediately.
* When running on the BB change the path of the ram temp file to a valid
  location.

Signed-off-by: Franklin S Cooper Jr <fcooper27@gmail.com>
Merge pull request #6952 from fcooper/master-bbb-support

Support ARM Linux device and add Beaglebone as a support device