OvmfPkg/build.sh: Add features and replace build32/64.sh

OvmfPkg/build.sh: Add features and replace build32/64.sh

Add a single build.sh to replace build32.sh & build64.sh.

The script watches for various parameters:
-a: allows selecting IA32 or X64 (default)
-b: allows selecting RELEASE or DEBUG (default)
-t: allows selecting the toolchain

When running qemu, the script doesn't always add -hda now.
If the user provides a disk parameter (for example, -fda, -hda
or -cdrom), then -hda will not be added to the qemu command line.

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@11238 6f19259b-4bc3-4df7-8a09-765794883524