Previously, we assumed that .rdata is zero-filled, so when writing
an COFF import table, we didn't write anything if the data is zero.
That assumption was wrong because .rdata can be merged with .text.
If .rdata is merged with .text, they are initialized with 0xcc, which
is a trap instruction.
This patch removes that assumption from code.
Should be merged to 8.0 branch as this is a regression.