[llvm] [MC][RISCV][LoongArch] Add AlignFragment size if layout is available and not need insert nops (PR #76552)

[Jinyang He via llvm-commits]

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@@ -64,8 +56,7 @@
 .word  .L2 - .L1
 .dword .L2 - .L1
 ## With relaxation, emit relocs because of the .align making the diff variable.
-## TODO Handle alignment directive. Why they emit relocs now? They returns
-## without folding symbols offset in AttemptToFoldSymbolOffsetDifference().
+## TODO Handle alignment directive.
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MQ-mengqing wrote:

I'll correct comment later. This `TODO` means alignment directive should generate R_LARCH_ALIGN, but now it does not.

https://github.com/llvm/llvm-project/pull/76552