builtin.closure: improove ppc64le closure if PIE

[tankf33der]

The lifetime of the ported ppc64le architecture in vlang is ~250 days.
All this time I remembered that closure crashes on debian13 (magic?).
When auditing inline assembler support, I ran into this crash again.
Debian13 - crashes, Almalinux9 - ok.

The issue turned out to be that Debian13 enabled PIE by default.
The compiled code relies on special register R12.

Picture below is PIE code. Right from the first lines the code relies on R12 and all calculations are based on it.

No R12 register if -no-pie.

I got access to such real hardware ppc64le with such Linux distributions:

CPU	Distro
Power10	AlmaLinux 9.7
Power9	Debian 13.2
Power9	AlmaLinux 8.10
Power8	Centos 7

Only Debian13 do PIE by default in this list.

Now VTEST_ONLY=closure ./v test vlib works everywhere in my tests.
After the merge I will check all servers from scratch again because right now there's a mess there and everything is torn apart.

This issue cost me 40 hours.

[spytheman]

Thank you a lot @tankf33der 🙇🏻 .

I am sorry about the time you lost debugging this.

On the bright side, you can think of it as saved time for everyone else that wanted to use V on that CPU, and for most people it would have been a lot longer, or even infinity.

[spytheman]

(the CI failure is unrelated and fixed on master)

[tankf33der]

VTEST_ONLY=closure ./v test vlib/

check report after merge:

Hardware	CPU	Distro
qemu	Power10	AlmaLinux 10.1
real	Power10	AlmaLinux 9.7
real	Power9	Debian 13.2
real	Power9	AlmaLinux 8.10
real	Power8	Centos 7

All ok.