LoongArch: Fix relaxation alignment with ld -r (PR 33236)

LoongArch has the same issue as RISC-V for PR 33236 [1].

Section alignment can't be adjusted for objects generated by ld -r.
If previous sections are relaxed, the subsequent section maybe misaligned.

To fix this, add an align section and an align relocation before each
section when ld -r. And change the section alignment to 4 to disable
the default section start address calculation.

ld.lld has fixed this issue in the following two patches [2] [3].

[1] https://sourceware.org/bugzilla/show_bug.cgi?id=33236
[2] https://github.com/llvm/llvm-project/pull/151639
[3] https://github.com/llvm/llvm-project/pull/198147