PR31208, strip can break ELF alignment requirements

In https://sourceware.org/pipermail/binutils/2007-August/053261.html
(git commit 3dea8fca) I disabled a then new linker feature that
removed empty PT_LOAD headers in cases where a user specified program
headers, and for objcopy.  This can be a problem for objcopy/strip and
since objcopy operates on sections, any part of a PT_LOAD loading file
contents not covered by a section will be omitted anyway.

	PR 31208
	* elf.c (_bfd_elf_map_sections_to_segments): Pass remove_empty_load
	as true to elf_modify_segment_map for objcopy/strip.

(cherry picked from commit 7f26d260)