BPF programs use single threaded LLD

[jackcmay]

Problem

Multi-threaded LLD is causing only partial relocation to take place. This results in what should be a double relocation (relocation of a symbol which contains an address that is also relocated) but only the first relocation is created correctly. The second relocation requires that an offset be written to the memory location being relocated, but that offset is zero in the final ELF. It's unclear why the LLD multi-threaded configuration is causing this issue and more investigation is warranted but not necessary at this time and will be time-consuming.

Summary of Changes

Use LLD in single-thread mode. There is very little performance impact since BPF programs include a small number of small object files.

The PR also pulls in rbpf changes that force a load failure if any invalid relocations are found.

Fixes #3108

[garious]

Also, consider dumping LLD. Though it's been around for awhile now, it's still the least proven component in the toolchain.

[jackcmay]

Thanks @garious , Will consider if this pops up again

[solana-grimes]

💔 Unable to automerge due to CI failure

[codecov]

Codecov Report

Merging #6088 into master will decrease coverage by 0.4%.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           master   #6088     +/-   ##
========================================
- Coverage    74.7%   74.3%   -0.5%     
========================================
  Files         226     238     +12     
  Lines       40660   42301   +1641     
========================================
+ Hits        30413   31431   +1018     
- Misses      10247   10870    +623