Broken link and misplaced comment in common.c

[SWilson4]

The link in the following comment is broken:

liboqs/src/common/common.c

Lines 40 to 45 in 4cc8884

	#if defined(OQS_DIST_X86_64_BUILD)
	/* set_available_cpu_extensions_x86_64() has been written using:
	* https://github.com/google/cpu_features/blob/master/src/cpuinfo_x86.c
	*/
	#include "x86_64_helpers.h"
	static void set_available_cpu_extensions(void) {

The comment currently on line 108 refers to the code currently at line 113 and should be moved for clarity.

liboqs/src/common/common.c

Lines 107 to 114 in 4cc8884

	static void set_available_cpu_extensions(void) {
	/* mark that this function has been called */
	cpu_ext_data[OQS_CPU_EXT_ARM_AES] = 1;
	cpu_ext_data[OQS_CPU_EXT_ARM_SHA2] = 1;
	cpu_ext_data[OQS_CPU_EXT_ARM_SHA3] = macos_feature_detection("hw.optional.armv8_2_sha3");
	cpu_ext_data[OQS_CPU_EXT_ARM_NEON] = macos_feature_detection("hw.optional.neon");
	cpu_ext_data[OQS_CPU_EXT_INIT] = 1;
	}

Reported by @trailofbits in Week 1 of their audit of liboqs.