On x86-64, PLT optimization does not require the binary to be linked
with -znow because indirect calls through GOT work correctly with lazy
binding. At runtime, the dynamic linker's resolver will populate the GOT
entry on the first call, just like with a regular PLT call.
This change removes the -znow requirement specifically for x86-64 while
keeping it for other architectures. I haven't checked RISV-V, but it's
still necessary on AArch64.
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