set path to linker script in %_package_note_file
    
    The package-notes feature¹ creates a linker script in %{buildsubdir}.
    Unfortunately, %{buildsubdir} is not set in %prep, leaving us with an
    incorrect path to the linker script.  The build then fails with:
    
       /usr/bin/ld: cannot open linker script file
       /builddir/build/BUILD/.package_note-git-2.35.0-0.2.rc2.fc36.3.x86_64.ld:
       No such file or directory
    
    Set the path to the linker script via %_package_note_file, per
    suggestion by Zbigniew Jędrzejewski-Szmek².
    
    References:
    ¹ https://fedoraproject.org/wiki/Changes/Package_information_on_ELF_objects
    ² https://bugzilla.redhat.com/2044028#c10