Fixes systemd build in Fedora rawhide.
The old ldsdir option is not useful, because both the directory and the
file name changed. Let's remove the option and try to autodetect the file
name. If this turns out to be not enough, a new option to simply specify
the full path to the file can be added.
F31:
efi arch: x86_64
EFI machine type: x64
EFI CC ccache cc
EFI lds: /usr/lib64/gnuefi/elf_x64_efi.lds
EFI crt0: /usr/lib64/gnuefi/crt0-efi-x64.o
EFI include directory: /usr/include/efi
F32:
efi arch: x86_64
EFI machine type: x64
EFI CC ccache cc
EFI lds: /usr/lib/gnuefi/x64/efi.lds
EFI crt0: /usr/lib/gnuefi/x64/crt0.o
EFI include directory: /usr/include/efi