[RISC-V] Fix linking problem

[broudy3]

Changed encoding in .cfi_personality in .macro NESTED_ENTRY from value 0x1C to value 0x1B.

When old encoding 0x1C is used in .cfi_personality :

• Clang/LLVM version 15/16 generates relocation R_RISCV_64 to symbol UnhandledExceptionHandlerUnix in file asmhelpers.S.o section .rela.eh_frame.
• LLD linker version 16 reports linking error about this:

ld.lld-16: error: relocation R_RISCV_64 cannot be used against symbol 'UnhandledExceptionHandlerUnix'; recompile with -fPIC
>>> defined in runtime/artifacts/obj/coreclr/linux.riscv64.Debug/vm/wks/CMakeFiles/cee_wks_core.dir/__/exceptionhandling.cpp.o
>>> referenced by runtime/artifacts/obj/coreclr/linux.riscv64.Debug/vm/wks/CMakeFiles/cee_wks_core.dir/__/riscv64/asmhelpers.S.o:(.eh_frame+0x11D6F6)

• LLD linker version 15, does not report error, instead it creates a invalid binary libcoreclr.so - first relocation in .rela.dyn points to some random code and 8 bytes from this code are replaced with address of UnhandledExceptionHandlerUnix, this corrupts the code and likely leads to application crash

When encoding 0x1B is used in .cfi_personality :

• Clang/LLVM version 15/16 (and also gcc I tested) generates relocation R_RISCV_32_PCREL to symbol UnhandledExceptionHandlerUnix in file asmhelpers.S.o section .rela.eh_frame.
• linking with LLD 15/16 is without error and compiled binary libcoreclr.so does not contain the problematic relocation which corrupts the code.

[broudy3]

@dotnet-policy-service agree

[jkotas]

Thanks

[clamp03]

Thank you