zld: adjust signed displacement source target addr
Previously, I mistakenly assumed that offset of the relocation
is enough when calculating relative offset of the target from the
source target section base address in case of section-based relocs
on x86_64. While this is true for `__TEXT,__text` section which
always starts at 0x0 in object files, this is absolutely not true
for `__TEXT,__StaticInit` section which will have nonzero base
address hence resulting in incorrect displacement calculations for
SIGNED relocs.
f67e756211Jakub Konka committed on 5/9/2021, 2:24:53 PMparent15d6efe