lto = 'fat' + RISCV interrupts results in changed binding to STB_GLOBAL linker errors

[MabezDev]

It seems this is specific to LTO.

• esp-riscv-rt defines cpu_int_x_handler as weak symbols
• esp-hal defines some cpu_int_x_handler handlers as global symbols to override the weak symbols for vectoring

It seems with lto = 'fat both the weakly linked symbols and the strong symbols end up in the same codegen unit and LLVM complains about the binding changing, but in reality the binding change is actually some global symbols that can resolve weaker ones.

[MabezDev]

Closed via #1327