mold 2.31.0 build failure when targeting ARMv6

[jpalus]

Build fails with

{standard input}: Assembler messages:
{standard input}:6254: Error: selected processor does not support `yield' in ARM mode

That's because of too optimistic change in 31969a2:

mold/common/common.h

Lines 526 to 532 in 2b67afb

	static inline void pause() {
	#if defined(__x86_64__)
	asm volatile("pause");
	#elif defined(__arm__) || defined(__aarch64__)
	asm volatile("yield");
	#endif
	}

The lowest ARM archs on which yield is available is ARM 6K or ARM 6M so it's missing on bare ARM 6 (-march=armv6) or lower. However __arm__ is defined on all ARM 32-bit.

[rui314]

Thank you for the report. I'll remove defined(__arm__) from the line. In the meantime, please apply a local patch to compile mold for arm.

[jpalus]

Simple alternative to still keep it for ARMv7 would be defined(__arm__) && defined(__ARM_ARCH) && __ARM_ARCH >= 7

[rui314]

Executing pause in this code path is not super important, and perhaps even more so on less powerful ARM processors, but let me try to do something for ARM.