BaseTools: Add missing Elf relocation type for LTO build

Add support to convert missing Elf relocation types
(R_X86_64_PLT32, R_X86_64_GOTPCREL, R_X86_64_REX_GOTPCRELX)
to PeCoff, which are required by LTO image.

These changes are necessary to unbreak sysutils/uefi-edk2-bhyve on
FreeBSD after the update of devel/binutils to version 2.31.1.

Special thanks to bap@FreeBSD.org to help me debug and find a
solution for this issue.

Reported by: many
Obtained from: https://github.com/M1cha/edk2/commit/86e401fd475eab7c74707edec3823fce06a686d9