llvm-readobj/ARM: activate big-endian attribute printing (#87806)

Activate attribute printing for big-endian encoding for ARM. The
supporting code already exists, and the patch is trivial.

Fixes #62400.

Author: artagnon

llvm/test/tools/llvm-readobj/ELF/ARM/attribute-big-endian.test

@@ -1,17 +1,23 @@
-## We only implement attribute section printing for little-endian encoding.
-
 # RUN: yaml2obj %s -o %t.o
-# RUN: llvm-readobj -A %t.o 2>&1 | FileCheck %s -DFILE=%t.o
+# RUN: llvm-readelf -A %t.o 2>&1 | FileCheck %s
 
-# CHECK: warning: '[[FILE]]': attribute printing not implemented for big-endian ARM objects
+# CHECK:      BuildAttributes {
+# CHECK-NEXT:   FormatVersion: 0x41
+# CHECK-NEXT:   Section 1 {
+# CHECK-NEXT:     SectionLength: 22
+# CHECK-NEXT:     Vendor: armabi
+# CHECK-NEXT:   }
+# CHECK-NEXT: }
 
 --- !ELF
 FileHeader:
   Class:   ELFCLASS32
-## Test big-endian encoding.
   Data:    ELFDATA2MSB
   Type:    ET_REL
   Machine: EM_ARM
 Sections:
   - Name: .ARM.attributes
     Type: SHT_ARM_ATTRIBUTES
+    ContentArray: [ 0x41, 0x00, 0x00, 0x00, 0x16, 0x61, 0x72, 0x6D, 0x61, 0x62,
+    0x69, 0x00, 0x01, 0x0b, 0x00, 0x00, 0x00, 0x04, 0x01, 0x06, 0x01, 0x08,
+    0x01 ]

llvm/tools/llvm-readobj/ELFDumper.cpp

@@ -2833,13 +2833,9 @@ template <class ELFT> void ELFDumper<ELFT>::printArchSpecificInfo() {
                     llvm::endianness::little);
     break;
   case EM_ARM:
-    if (Obj.isLE())
-      printAttributes(ELF::SHT_ARM_ATTRIBUTES,
-                      std::make_unique<ARMAttributeParser>(&W),
-                      llvm::endianness::little);
-    else
-      reportUniqueWarning("attribute printing not implemented for big-endian "
-                          "ARM objects");
+    printAttributes(
+        ELF::SHT_ARM_ATTRIBUTES, std::make_unique<ARMAttributeParser>(&W),
+        Obj.isLE() ? llvm::endianness::little : llvm::endianness::big);
     break;
   case EM_RISCV:
     if (Obj.isLE())