riscv: fix vdso build with lld

When building with the LLVM linker this error occurrs:
    LD      arch/riscv/kernel/vdso/vdso-syms.o
  ld.lld: error: no input files

This happens because the lld treats -R as an alias to -rpath, as opposed
to ld where -R means --just-symbols.

Use the long option name for compatibility between the two.

Link: ClangBuiltLinux#805
Reported-by: Dmitry Golovin <[email protected]>
Reviewed-by: Nick Desaulniers <[email protected]>
Signed-off-by: Ilie Halip <[email protected]>
Reviewed-by: Fangrui Song <[email protected]>
Signed-off-by: Palmer Dabbelt <[email protected]>

Author: ihalip

arch/riscv/kernel/vdso/Makefile

@@ -33,15 +33,15 @@ $(obj)/vdso.so.dbg: $(src)/vdso.lds $(obj-vdso) FORCE
 	$(call if_changed,vdsold)
 
 # We also create a special relocatable object that should mirror the symbol
-# table and layout of the linked DSO.  With ld -R we can then refer to
-# these symbols in the kernel code rather than hand-coded addresses.
+# table and layout of the linked DSO. With ld --just-symbols we can then
+# refer to these symbols in the kernel code rather than hand-coded addresses.
 
 SYSCFLAGS_vdso.so.dbg = -shared -s -Wl,-soname=linux-vdso.so.1 \
 	-Wl,--build-id -Wl,--hash-style=both
 $(obj)/vdso-dummy.o: $(src)/vdso.lds $(obj)/rt_sigreturn.o FORCE
 	$(call if_changed,vdsold)
 
-LDFLAGS_vdso-syms.o := -r -R
+LDFLAGS_vdso-syms.o := -r --just-symbols
 $(obj)/vdso-syms.o: $(obj)/vdso-dummy.o FORCE
 	$(call if_changed,ld)