xen: Fix EFI buildid alignment

Old binutils get confused about .buildid overlapping (in VA space) with
earlier section. That confusion results in weird errors down the road,
like this one:

    objcopy: xen.efi: Data Directory size (1c) exceeds space left in section (8)

While the bug is fixed in later binutils version, force alignment of the
buildid to avoid overlapping and make it work with older versions too.
This can be reverted once toolchain base is raised at or above binutils
2.36.

Details at https://lore.kernel.org/xen-devel/3TMd7J2u5gCA8ouIG_Xfcw7s5JKMG06XsDIesEB3Fi9htUJ43Lfl057wXohlpCHcszqoCmicpIlneEDO26ZqT8QfC2Y39VxBuqD3nS1j5Q4=@trmm.net/T/#u

Fixes: eee5909e9d ("x86/EFI: use less crude a way of generating the build ID")
Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
master commit: 26b111cc22
master date: 2025-11-20 14:29:57 +0000

xen/arch/x86/xen.lds.S

@@ -173,6 +173,8 @@ SECTIONS
        __note_gnu_build_id_end = .;
   } PHDR(note) PHDR(text)
 #elif defined(BUILD_ID_EFI)
+  /* Workaround bug in binutils < 2.36 */
+  . = ALIGN(32);
   DECL_SECTION(.buildid) {
        __note_gnu_build_id_start = .;
        *(.buildid)