arm64: Handle .ARM.attributes section in linker scripts

A recent LLVM commit [1] started generating an .ARM.attributes section
similar to the one that exists for 32-bit, which results in orphan
section warnings (or errors if CONFIG_WERROR is enabled) from the linker
because it is not handled in the arm64 linker scripts.

  ld.lld: error: arch/arm64/kernel/vdso/vgettimeofday.o:(.ARM.attributes) is being placed in '.ARM.attributes'
  ld.lld: error: arch/arm64/kernel/vdso/vgetrandom.o:(.ARM.attributes) is being placed in '.ARM.attributes'

  ld.lld: error: vmlinux.a(lib/vsprintf.o):(.ARM.attributes) is being placed in '.ARM.attributes'
  ld.lld: error: vmlinux.a(lib/win_minmax.o):(.ARM.attributes) is being placed in '.ARM.attributes'
  ld.lld: error: vmlinux.a(lib/xarray.o):(.ARM.attributes) is being placed in '.ARM.attributes'

Discard the new sections in the necessary linker scripts to resolve the
warnings, as the kernel and vDSO do not need to retain it, similar to
the .note.gnu.property section.

Cc: [email protected]
Fixes: b3e5d80 ("arm64/build: Warn on orphan section placement")
Link: llvm/llvm-project@ee99c4d [1]
Signed-off-by: Nathan Chancellor <[email protected]>
Link: https://lore.kernel.org/r/20250206-arm64-handle-arm-attributes-in-linker-script-v3-1-d53d169913eb@kernel.org
Signed-off-by: Will Deacon <[email protected]>

Author: nathanchance

arch/arm64/kernel/vdso/vdso.lds.S

@@ -41,6 +41,7 @@ SECTIONS
 	 */
 	/DISCARD/	: {
 		*(.note.GNU-stack .note.gnu.property)
+		*(.ARM.attributes)
 	}
 	.note		: { *(.note.*) }		:text	:note
 

arch/arm64/kernel/vmlinux.lds.S

@@ -162,6 +162,7 @@ SECTIONS
 	/DISCARD/ : {
 		*(.interp .dynamic)
 		*(.dynsym .dynstr .hash .gnu.hash)
+		*(.ARM.attributes)
 	}
 
 	. = KIMAGE_VADDR;