[lld][COFF] Remove duplicate strtab entries (#141197)
String table size is too big for large binary when symbol table is
enabled. Some strings in strtab is same so it can be reused.
This patch revives 9ffeaaa authored by mstorsjo with the prioritized
string table builder to fix debug section name issue (see 4d2eda2
for more details).
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Co-authored-by: Wen Haohai <whh108@live.com>
Co-authored-by: James Henderson <James.Henderson@sony.com>
