[llvm] [llvm-objdump][ELF]Fix crash when reading strings from .dynstr(#86612) (PR #125679)

[Fangrui Song via llvm-commits]

================
@@ -470,3 +473,34 @@ Sections:
        Value: 0x1
      - Tag:   DT_NULL
        Value: 0x0
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_EXEC
+  Machine: EM_X86_64
+Sections:
+  - Name:    .dynstr
+    Type:    SHT_STRTAB
+    Address: 0x1000
+    Size:    0x10
+    Content: "004400550066007700"
+  - Name: .dynamic
+    Type: SHT_DYNAMIC
+    Entries:
+     - Tag:   DT_NEEDED
+       Value: 0x1245657656
+     - Tag:   DT_STRTAB
+       Value: 0x1000
+     - Tag:   DT_NULL
+       Value: 0x0
+ProgramHeaders:
+  - Type:     PT_LOAD
+    VAddr:    0x1000
+    FirstSec: .dynstr
+    LastSec:  .dynamic
+  - Type:     PT_DYNAMIC
+    VAddr:    0x101D
+    FirstSec: .dynamic
+    LastSec:  .dynamic
----------------
MaskRay wrote:

The icon shows that there is no EOL at the end of the test. Please fix it.

https://github.com/llvm/llvm-project/pull/125679