Set up default shstrtab entries at initialization

[emaste]

Summary

If we use -R to remove all sections we still need a .shstrtab (which will itself be the only section entry). Do not wait until the addition of the first non-default entry to create the default ones.

Elftoolchain ticket 463
https://sourceforge.net/p/elftoolchain/tickets/463/

Test Plan

touch empty.s
make empty.o
strip -o empty-stripped.o -R .text -R .data -R .bss -R .ARM.attributes -R .reginfo -R .gnu.attributes -R .MIPS.abiflags -R .pdr -R .xtensa.info empty.o
readelf -S empty-stripped.o

[imp]

I believe this is OK...

[emaste]

Closed by commit rS276061 (authored by @emaste).