ld: aarch64: make EH Frame parsing aware of augmentation char 'G'

ld: aarch64: make EH Frame parsing aware of augmentation char 'G'

As per the DWARF for the Arm 64-bit Architecture (AArch64)
specification, the augmentation char 'G' indicates that associated
frames may modify MTE tags on the stack space they use.

Add knowledge of the 'G' augmentation char to the EH Frame parsing
code.

ChangeLog:

        * bfd/elf-eh-frame.c (_bfd_elf_parse_eh_frame): Accommodate
	augmentation char 'G'.
        * ld/testsuite/ld-aarch64/aarch64-elf.exp: New test.
        * ld/testsuite/ld-aarch64/mte-tagged-frame-bar.s: New test.
        * ld/testsuite/ld-aarch64/mte-tagged-frame-foo.s: New test.
        * ld/testsuite/ld-aarch64/mte-tagged-frame.d: New test.