With commit f0b2132b35 ("ld.so:
Support moving versioned symbols between sonames [BZ #24741]"), the
dynamic linker will find the definition of vfork in libc and binds
a vfork reference to that symbol, even if the soname in the version
reference says that the symbol should be located in libpthread.
As a result, the forwarder (whether it's IFUNC-based or a duplicate
of the libc implementation) is no longer necessary.
On older architectures, a placeholder symbol is required, to make sure
that the GLIBC_2.1.2 symbol version does not go away, or is turned in
to a weak symbol definition by the link editor. (The symbol version
needs to preserved so that the symbol coverage check in
elf/dl-version.c does not fail for old binaries.)
mips32 is an outlier: It defined __vfork@@GLIBC_2.2, but the
baseline is GLIBC_2.0. Since there are other @@GLIBC_2.2 symbols,
the placeholder symbol is not needed there.
