[lld] [LLD][ELF][RISCV][Zicfilp][Zicfiss] Support `-z zicfilp=` and `-z zicfiss=` to force enable/disable features (PR #143114)

[Fangrui Song via llvm-commits]

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@@ -12,14 +13,20 @@
 # RUN: llvm-mc --filetype=obj --triple=riscv64 f2-s.s -o f2-s.o
 # RUN: llvm-mc --filetype=obj --triple=riscv64 f3.s   -o f3.o
 # RUN: llvm-mc --filetype=obj --triple=riscv64 f3-s.s -o f3-s.o
+# RUN: llvm-mc --filetype=obj --triple=riscv64 f3-u.s -o f3-u.o
 
-## ZICFILP-func-sig should be enabled when it's enabled in all inputs
+## ZICFILP-func-sig should be enabled when it's enabled in all inputs or when
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MaskRay wrote:

End complete sentences in comments with a full stop.

https://github.com/llvm/llvm-project/pull/143114