[ELF] --pack-dyn-relocs=android+relr: place IRELATIVE in .rela.plt (#86751)

Current Bionic processes relocations in this order:

* DT_ANDROID_REL[A]
* DT_RELR
* DT_REL[A]
* DT_JMPREL

If an IRELATIVE relocation is in DT_ANDROID_REL[A], it would read
unrelocated (incorrect) global variables associated with RELR when
--pack-dyn-relocs=android+relr is enabled. Work around this by placing
IRELATIVE in .rel[a].plt (DT_JMPREL).

Link: https://r.android.com/3014185