Fix unwind from signal handler

[azat]

In case of this is frame of signal handler, the IP should be incremented, because the IP saved in the signal handler points to first non-executed instruction, while FDE/CIE expects IP to be after the first non-executed instruction.

PR in upstream: llvm/llvm-project#92291

[alexey-milovidov]

This can point in the middle between two instructions. Is this ok?

[azat]

This is only needed to execute proper CFI here -

libunwind/src/DwarfParser.hpp

Lines 430 to 434 in 854538c

	ParseInfo parseInfoArray[] = {
	{cieInfo.cieInstructions, cieInfo.cieStart + cieInfo.cieLength,
	(pint_t)(-1)},
	{fdeInfo.fdeInstructions, fdeInfo.fdeStart + fdeInfo.fdeLength,
	upToPC - fdeInfo.pcStart}};

So in other words, everything should be OK

[alexey-milovidov]

Let's give it a try.