PE/COFF exporter: Save the first relocation and write it to the end of the relocations if we have more than 64k relocations.
In that case we need to set IMAGE_SCN_LNK_NRELOC_OVFL in the section header and the first relocation contains the real
number of relocations. Previously a null relocation was written at the start and overwritten if necessary but GCC ld
2.35.1 didn't like this.