valgrind + llvm10

I did some bisecting and it seems that the update to clang 10 broke
valgrind. Specifically /usr/local/lib/valgrind/memcheck-amd64-openbsd:

$ ktrace -i /usr/local/lib/valgrind/memcheck-amd64-openbsd
Abort trap
$ kdump
12913 ktrace RET ktrace 0
12913 ktrace CALL execve(0x7f7ffffc6fca,0x7f7ffffc6e68,0x7f7ffffc6e78)
12913 ktrace NAMI "/usr/local/lib/valgrind/memcheck-amd64-openbsd"
12913 ktrace ARGS
[0] = "/usr/local/lib/valgrind/memcheck-amd64-openbsd"

Compiling valgrind with CC=gcc gives the same result, so my guess is
that the linker does something unexpected.

martijn@