ELFYAML: Enable parsing of EM_AMDGPU

[silvas]

Not sure it is worth adding the test just to verify that we can type the same thing in two places, but LGTM. If you have the time, it would be nice to split this out into a .def file like we have done in include/llvm/Support/ELFRelocs, so then we can derive both from the same single point of truth.

[silvas]

Forgot to hit "accept".

lib/Object/ELFYAML.cpp

#define ECase(X) IO.enumCase(Value, #X, ELF::X);
   ECase(EM_COREA_1ST)
   ECase(EM_COREA_2ND)
   ECase(EM_ARC_COMPACT2)
   ECase(EM_OPEN8)
   ECase(EM_RL78)
   ECase(EM_VIDEOCORE5)
   ECase(EM_78KOR)
   ECase(EM_56800EX)
+  ECase(EM_AMDGPU)
 #undef ECase
 }
 
 void ScalarEnumerationTraits<ELFYAML::ELF_ELFCLASS>::enumeration(
     IO &IO, ELFYAML::ELF_ELFCLASS &Value) {
 #define ECase(X) IO.enumCase(Value, #X, ELF::X);
   // Since the semantics of ELFCLASSNONE is "invalid", just don't accept it
   // here.

test/Object/AMDGPU/elf-definitios.yaml

+# RUN: yaml2obj -format=elf %s > %t.o
+# RUN: llvm-readobj -file-headers %t.o | FileCheck %s
+
+# CHECK:  Machine: EM_AMDGPU (0xE0)
+
+---
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_REL
+  Machine: EM_AMDGPU
+...