Use '-g' instead of '-g3' when compiling grub2.
    
    The rpm-build's "debugedit" program will silently corrupt .debug_macro
    strings when a binary is compiled with -g3.  Later in the build phase,
    gdb-add-index is invoked to extract the DWARF index from the binary,
    and GDB will segfault because dwarf2read.c:parse_definition_macro's
    'body' variable is NULL.
    
    Resolves: rhbz#1708780