rtld: add .cfi_undefined lr to rtld_start.S on powerpc*HEADmain

Without it, LLVM libunwind doesn't know where to stop when unwinding the
main thread, so it uses a stale LR as the return address and crashes.
Our libunwind doesn't do that since 5866c369e4fd reverted it, but
programs that bundle their own copy, like ClickHouse, are hit by it.

amd64, arm64, i386 and riscv already have the same annotation.

Approved by:	jhibbits
MFC after:	1 week
Differential Revision:	https://reviews.freebsd.org/D60740

0 files changed, 0 insertions, 0 deletions