[lldb] [test] Fix DW_TAG_GNU_call_site-DW_AT_low_pc.s relocation

I have made the DW_FORM_ref4 relative. One could also use relocated
DW_FORM_ref_addr instead.

Tested with:
        echo 'void f(){}'|clang -o 1.o -c -Wall -g -x c -;./bin/clang -o 1 1.o ../llvm-monorepo/lldb/test/Shell/SymbolFile/DWARF/DW_TAG_GNU_call_site-DW_AT_low_pc.s;./bin/lldb --no-lldbinit ./1 -o r -o 'p p' -o exit