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.