binutils* testsuite/lib/binutils-common.exp (is_elf_format): Add avr-*-*.
ld * testsuite/ld-elf/pr18735.d: Allow other symbols.
* testsuite/ld-elf/sec64k.exp: Skip 64ksec for avr.
* testsuite/ld-gc/pr14265.d: Allow other symbols.
* testsuite/ld-plugin/plugin.exp: Add PR ld/17973 to
plugin_tests only if check_shared_lib_support is true.
* testsuite/ld-selective/selective.exp: Add --section-start
flag for avr.