[llvm-objcopy] Use the full filename in --add-gnu-debuglink

[arichardson]

Summary

The current implementation was writing the file name without the extension
whereas GNU objcopy writes the full filename. With this change GDB will now
load the .debug file instead of silently ignoring it.

[jakehehrlich]

LGTM

I realized this a little while back but never got around to fixing it. Thanks!

test/tools/llvm-objcopy/add-gnu-debuglink.test

FileHeader:
   Machine:         EM_X86_64
 
 # CHECK:       Name: .gnu_debuglink
 # CHECK-NEXT:  Type: SHT_PROGBITS (0x1)
 # CHECK-NEXT:  Flags [ (0x0)
 # CHECK-NEXT:  ]
 # CHECK-NEXT:  Address: 0x0
 # CHECK-NEXT:  Offset:
-# CHECK-NEXT:  Size: 32
+# CHECK-NEXT:  Size: 36
 # CHECK-NEXT:  Link: 0
 # CHECK-NEXT:  Info: 0
 # CHECK-NEXT:  AddressAlignment: 4
 # CHECK-NEXT:  EntrySize: 0
 # CHECK-NEXT:  SectionData (
 # CHECK-NEXT:      0000: 6164642D 676E752D 64656275 676C696E  |add-gnu-debuglin|
-# CHECK-NEXT:      0010: 6B2E7465 73742E74 6D700000 72C49B0C  |k.test.tmp..r...|
+# CHECK-NEXT:      0010: 6B2E7465 73742E74 6D702E62 6C6F6200  |k.test.tmp.blob.|
+# CHECK-NEXT:      0020: 72C49B0C                             |r...|
 # CHECK-NEXT:  )

tools/llvm-objcopy/Object.cpp

error("Link field value " + Twine(Link) + " in section " + Name +
           " is not a string table");
   }
   setStrTab(StrTab);
 }
 
 void SectionWithStrTab::finalize() { this->Link = StrTab->Index; }
 
 void GnuDebugLinkSection::init(StringRef File, StringRef Data) {
-  FileName = sys::path::stem(File);
-  // The format for the .gnu_debuglink starts with the stemmed file name and is
+  FileName = sys::path::filename(File);
+  // The format for the .gnu_debuglink starts with the file name and is
   // followed by a null terminator and then the CRC32 of the file. The CRC32
   // should be 4 byte aligned. So we add the FileName size, a 1 for the null
   // byte, and then finally push the size to alignment and add 4.
   Size = alignTo(FileName.size() + 1, 4) + 4;
   // The CRC32 will only be aligned if we align the whole section.
   Align = 4;
   Type = ELF::SHT_PROGBITS;
   Name = ".gnu_debuglink";