aarch64: Accept PLT calls to __getauxval within libc.so

When using outline atomics (-moutline-atomics, the default for ARMv8-A
starting with GCC 10), libgcc contains an ELF constructor which calls
__getauxval.  This code is built outside of glibc, so none of its
internal PLT avoidance schemes can be applied to it.  This change
suppresses the elf/check-localplt failure.