bfd * elf-bfd.h: Add callback to count additional relocations.
* elf32-arm.c (_arm_elf_section_data): Add new counter.
(insert_cantunwind_after): Increment relocations counter.
(elf32_arm_fix_exidx_coverage): Remove exidx entries and add
terminating CANTUNWIND entry only in final builds.
(elf32_arm_add_relocation): New function.
(elf32_arm_write_section): Add relocations in relocatable builds.
(elf32_arm_count_additional_relocs): New function.
(elf_backend_count_additional_relocs): New define.
* bfd/elflink.c (bfd_elf_final_link): Use callback and adjust size of
.rel section.
* bfd/elfxx-target.h (elf_backend_count_additional_relocs): New define.
ld * emultempl/armelf.em (gld${EMULATION_NAME}_after_allocation): Call
elf32_arm_fix_exidx_coverage for relocatable builds.
ld/testsuite
* ld-arm/arm-elf.exp: New test.
* ld-arm/unwind-rel.d: New file.
* ld-arm/unwind-rel1.s: New file.
* ld-arm/unwind-rel2.s: New file.
* ld-arm/unwind-rel3.s: New file.
