[yaml2obj] Support PT_GNU_STACK and PT_GNU_RELRO

[MaskRay]

Summary

PT_GNU_STACK is used in an llvm-objcopy test.

I plan to use PT_GNU_RELRO in a patch to improve nested segment
processing in llvm-objcopy (PR42963).

[grimar]

LGTM

[MaskRay]

Update a test test/tools/llvm-objcopy/ELF/marker-segment.test to use PT_GNU_STACK
Add numbers beside Type: PT_*

lib/ObjectYAML/ELFYAML.cpp

#define ECase(X) IO.enumCase(Value, #X, ELF::X)
   ECase(PT_LOAD);
   ECase(PT_DYNAMIC);
   ECase(PT_INTERP);
   ECase(PT_NOTE);
   ECase(PT_SHLIB);
   ECase(PT_PHDR);
   ECase(PT_TLS);
   ECase(PT_GNU_EH_FRAME);
+  ECase(PT_GNU_STACK);
+  ECase(PT_GNU_RELRO);
 #undef ECase
   IO.enumFallback<Hex32>(Value);
 }
 
 void ScalarEnumerationTraits<ELFYAML::ELF_EM>::enumeration(
     IO &IO, ELFYAML::ELF_EM &Value) {
 #define ECase(X) IO.enumCase(Value, #X, ELF::X)
   ECase(EM_NONE);

test/tools/yaml2obj/program-header.yaml

Sections:
       - Section: .text
       - Section: .init
   - Type: PT_LOAD
     Flags: [ PF_R ]
     VAddr: 0xAAAA2000
     PAddr: 0xFFFF2000
     Sections:
       - Section: .data
+  - Type: PT_GNU_EH_FRAME
+  - Type: PT_GNU_STACK
+  - Type: PT_GNU_RELRO
 
 #CHECK:     ProgramHeaders [
 #CHECK-NEXT:   ProgramHeader {
 #CHECK-NEXT:    Type: PT_LOAD
 #CHECK-NEXT:    Offset: 0x1000
 #CHECK-NEXT:    VirtualAddress: 0xAAAA1000
 #CHECK-NEXT:    PhysicalAddress: 0xFFFF1000
 #CHECK-NEXT:    FileSize: 20

 #CHECK-NEXT:    PhysicalAddress: 0xFFFF2000
 #CHECK-NEXT:    FileSize: 4
 #CHECK-NEXT:    MemSize: 4
 #CHECK-NEXT:    Flags [
 #CHECK-NEXT:      PF_R
 #CHECK-NEXT:    ]
 #CHECK-NEXT:    Alignment: 4096
 #CHECK-NEXT:  }
+#CHECK-NEXT:  ProgramHeader {
+#CHECK-NEXT:    Type: PT_GNU_EH_FRAME
+#CHECK:       }
+#CHECK-NEXT:  ProgramHeader {
+#CHECK-NEXT:    Type: PT_GNU_STACK
+#CHECK:       }
+#CHECK-NEXT:  ProgramHeader {
+#CHECK-NEXT:    Type: PT_GNU_RELRO
+#CHECK:       }
 #CHECK-NEXT:]
 
 ## Check we do not allow referencing sections that do not exist.
 # RUN: not yaml2obj --docnum=2 %s -o %t 2>&1 | FileCheck %s --check-prefix=ERR
 # ERR: error: Unknown section referenced: '.foo' by program header.
 
 --- !ELF
 FileHeader:
   Class:           ELFCLASS64
   Data:            ELFDATA2LSB
   Type:            ET_EXEC
   Machine:         EM_X86_64
 ProgramHeaders:
   - Type: PT_LOAD
     Sections:
       - Section: .foo