[LLD][ELF] - Convert symbol-index.s testcase to a YAML test case. NFCI.

This removes one more binary object from the inputs and fixes the
test case description.

Previously it said that:
"symbol-index.elf has incorrect type of .symtab section.
There is no symbol bodies because of that and any symbol index becomes incorrect."

But the real reason of the failture was not the incorrect type of a symbol table,
but invalid index of the symbol used in a relocation, what happened because
previous test tried to read .symtab as a SHT_RELA section.

llvm-svn: 359197

Author: George Rimar

lld/test/ELF/invalid/Inputs/symbol-index.elf

@@ -49,3 +49,28 @@ Sections:
 Symbols:         
   - Name:        foo
     Binding:     STB_GLOBAL
+
+## Relocation refers to a symbol with index larger than
+## symbol table size. Check we report it.
+# RUN: yaml2obj -docnum=3 %s -o %t2.o
+# RUN: not ld.lld %t2.o -o %t2 2>&1 | FileCheck %s --check-prefix=ERR3
+# ERR3: error: {{.*}}.o: invalid symbol index
+
+--- !ELF
+FileHeader:
+  Class:         ELFCLASS64
+  Data:          ELFDATA2LSB
+  Type:          ET_REL
+  Machine:       EM_X86_64
+Sections:
+  - Name:        .text
+    Type:        SHT_PROGBITS
+    Flags:       [ SHF_ALLOC, SHF_EXECINSTR ]
+  - Name:        .rela.text
+    Type:        SHT_RELA
+    Link:        .symtab
+    Info:        .text
+    Relocations:
+      - Offset:  0x0000000000000000
+        Symbol:  255
+        Type:    R_X86_64_64