Emit *GLOB_DAT instead of *RELATIVE relocs for protected data
in shared objects.
This is needed for the fix of glibc bug 17711:
https://sourceware.org/bugzilla/show_bug.cgi?id=17711
bfd:
PR ld/18705
* elf32-arm.c (elf_backend_extern_protected_data): Define.
ld/testsuite:
PR ld/18705
* ld-arm/protected-data.d: New.
* ld-arm/protected-data.s: New.
* ld-arm/arm-elf.exp: Add new test.
