LoongArch: Fix DT_RELR and relaxation interaction

Due to the way BFD implements DT_RELR as a part of relaxation, if in a
relax trip size_relative_relocs has changed the layout, when
relax_section runs only the vma of the section being relaxed is
guaranteed to be updated.  Then bad thing can happen.  For example, when
linking an auxilary program _freeze_module in the Python 3.12.4 building
system (with PGO + LTO), before sizing the .relr.dyn section, the vma of
.text is 30560 and the vma of .rodata is 2350944; in the final
executable the vma of .text is 36704 and the vma of .rodata is 2357024.
The vma increase is expected because .relr.dyn is squashed somewhere
before .text.  But size_relative_relocs may see the state in which .text
is at 36704 but .rodata "is" still at 2350944.  Thus the distance
between .text and .rodata can be under-estimated and overflowing
R_LARCH_PCREL20_S2 reloc can be created.

To avoid this issue, if size_relative_relocs is updating the size of
.relr.dyn, just supress the normal relaxation in this relax trip.  In
this situation size_relative_relocs should have been demending the next
relax trip, so the normal relaxation can happen in the next trip.

I tried to make a reduced test case but failed.

Signed-off-by: Xi Ruoyao <xry111@xry111.site>