Zixuan Wang authored Oct 04, 2021 and Paolo Bonzini committed Oct 31, 2021

This commit provides initial support for x86 test cases to boot from
UEFI:

   1. UEFI compiler flags are added to Makefile
   2. A new TARGET_EFI macro is added to turn on/off UEFI startup code
   3. Previous Multiboot setup code is refactored and updated for
      supporting UEFI, including the following changes:
      1. x86/efi/crt0-efi-x86_64.S: provides entry point and jumps to
         setup code in lib/efi.c.
      2. lib/efi.c: performs UEFI setup, calls arch-related setup
         functions, then jumps to test case main() function
      3. lib/x86/setup.c: provides arch-related setup under UEFI

To build test cases for UEFI, please first install the GNU-EFI library.
Check x86/efi/README.md for more details.

This commit is tested by a simple test calling report() and
report_summayr(). This commit does not include such a test to avoid
unnecessary files added into git history. To build and run this test in
UEFI (assuming file name is x86/dummy.c):

   ./configure --target-...