[yaml2obj] - Allow using an arbitrary value for OSABI.

[grimar]

Summary

There was no way to set an unsupported or unknown OS ABI.
With this patch it is possible to use any numeric value.

Depends on: https://reviews.llvm.org/D71764

[jhenderson]

LGTM.

llvm/lib/ObjectYAML/ELFYAML.cpp

#define ECase(X) IO.enumCase(Value, #X, ELF::X)
   ECase(ELFOSABI_AMDGPU_HSA);
   ECase(ELFOSABI_AMDGPU_PAL);
   ECase(ELFOSABI_AMDGPU_MESA3D);
   ECase(ELFOSABI_ARM);
   ECase(ELFOSABI_C6000_ELFABI);
   ECase(ELFOSABI_C6000_LINUX);
   ECase(ELFOSABI_STANDALONE);
 #undef ECase
+  IO.enumFallback<Hex8>(Value);
 }
 
 void ScalarBitSetTraits<ELFYAML::ELF_EF>::bitset(IO &IO,
                                                  ELFYAML::ELF_EF &Value) {
   const auto *Object = static_cast<ELFYAML::Object *>(IO.getContext());
   assert(Object && "The IO context is not initialized");
 #define BCase(X) IO.bitSetCase(Value, #X, ELF::X)
 #define BCaseMask(X, M) IO.maskedBitSetCase(Value, #X, ELF::X, ELF::M)

llvm/test/tools/yaml2obj/ELF/header-osabi.yaml

 
 --- !ELF
 FileHeader:
   Class:   ELFCLASS64
   Data:    ELFDATA2LSB
   Type:    ET_REL
   Machine: EM_X86_64
   OSABI:   ELFOSABI_STANDALONE
+
+## Test we can use an arbitrary number for OSABI.
+# RUN: yaml2obj %s --docnum=27 -o %t.number
+# RUN: llvm-readobj --file-headers %t.number | FileCheck %s --check-prefix=OSABI-NUMBER
+# OSABI-NUMBER: OS/ABI: 0xFE
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_REL
+  Machine: EM_X86_64
+  OSABI:   0xFE