[DWARFYAML] Add support for emitting multiple abbrev tables.

This patch adds support for emitting multiple abbrev tables. Currently,
compilation units will always reference the first abbrev table.

Reviewed By: jhenderson, labath

Differential Revision: https://reviews.llvm.org/D86194

llvm/test/tools/yaml2obj/ELF/DWARF/debug-info.yaml

@@ -902,3 +902,24 @@ DWARF:
         - AbbrCode: 1
           Values:
             - Value: 0x1234
+
+## n) Test that yaml2obj emits an error message when a compilation unit has values but there is no associated abbrev table.
+
+## RUN: not yaml2obj --docnum=16 %s 2>&1 | FileCheck %s --check-prefix=NO-ABBREV
+
+# NO-ABBREV: yaml2obj: error: non-empty compilation unit should have an associated abbrev table
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_EXEC
+  Machine: EM_X86_64
+DWARF:
+  debug_info:
+    - Version:    4
+      AbbrOffset: 0x00
+      Entries:
+        - AbbrCode: 1
+          Values:
+            - Value: 0x1234