Some of the symbols listed in PLATFORM_SYMBOLS are not only specific
to Linux, but rather specific to the GNU toolchain. Hence, use them
when inspecting ELF binaries produced by a GNU toolchain: this means
on Hurd ('GNU'), and on e.g. kFreeBSD ('GNU/kFreeBSD').
Signed-off-by: Pino Toscano <toscano.pino@tiscali.it>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/21825>