vdso32: Invoke clang with correct path to GCC toolchain

Clang needs to have access to a GCC toolchain which we advertise using
the command line option --gcc-toolchain=. Clang previously picked the
wrong toolchain which resulted in the following error message:

/..//bin/as: unrecognized option '-EL'

Bug: 123422077
Signed-off-by: Daniel Mentz <danielmentz@google.com>
Change-Id: I3e339dd446b71e2c75eb9e2c186eba715b3771cd
Signed-off-by: khusika <khusikadhamar@gmail.com>