Adding XR Hands

[GlebThePolar]

What I did to add XR Hands

Added package XR Hands (com.unity.xr.hands). Versions:
com.unity.xr.hands 1.8.0 (com.unity.xr.openxr 1.16.1)

Also I have PICO Integrations since I target both Quest 3 pro and Pico 4 ultra
com.unity.xr.picoxr 3.4.0 (Git)

Updated meta data for Packages/com.unity.xr.hands/Runtime/android/x64/libUnityOpenXRHands.so

Include Platforms -- enabled Editor and Standalone (but probably only Editor is needed)
Platform settings -- Editor -- OS = Linux, CPU x64
Standalone -- Linux x64

If you do it in Editor then don't forget to apply with button

On this stage I had "DLL not found" critical error. I found same problems as with OpenXR x86_64 native binary: the LIBC/GLIBC tags conflict

To fix I patched NativeFix/compat_libc.c -- added missing things (used ChatGPT for this)
In includes added this:
#include <strings.h>

In section "String functions":

char *compat_strstr(const char *haystack, const char *needle) {
    return strstr(haystack, needle);
}
__asm__(".symver compat_strstr, strstr@LIBC");

char *compat_strchr(const char *s, int c) {
    return strchr(s, c);
}
__asm__(".symver compat_strchr, strchr@LIBC");

char *compat_strrchr(const char *s, int c) {
    return strrchr(s, c);
}
__asm__(".symver compat_strrchr, strrchr@LIBC");

size_t compat_strcspn(const char *s, const char *reject) {
    return strcspn(s, reject);
}
__asm__(".symver compat_strcspn, strcspn@LIBC");

size_t compat_strspn(const char *s, const char *accept) {
    return strspn(s, accept);
}
__asm__(".symver compat_strspn, strspn@LIBC");

char *compat_strdup(const char *s) {
    return strdup(s);
}
__asm__(".symver compat_strdup, strdup@LIBC");

In section "stdlib":

void *compat_calloc(size_t nmemb, size_t size) {
    return calloc(nmemb, size);
}
__asm__(".symver compat_calloc, calloc@LIBC");

char *compat_getenv(const char *name) {
    return getenv(name);
}
__asm__(".symver compat_getenv, getenv@LIBC");

int compat_putenv(char *string) {
    return putenv(string);
}
__asm__(".symver compat_putenv, putenv@LIBC");

int compat_setenv(const char *name, const char *value, int overwrite) {
    return setenv(name, value, overwrite);
}
__asm__(".symver compat_setenv, setenv@LIBC");

int compat_unsetenv(const char *name) {
    return unsetenv(name);
}
__asm__(".symver compat_unsetenv, unsetenv@LIBC");

int compat_pthread_create(
    pthread_t *thread,
    const pthread_attr_t *attr,
    void *(*start_routine)(void *),
    void *arg)
{
    return pthread_create(thread, attr, start_routine, arg);
}
__asm__(".symver compat_pthread_create, pthread_create@LIBC");

void compat_pthread_exit(void *retval) {
    pthread_exit(retval);
}
__asm__(".symver compat_pthread_exit, pthread_exit@LIBC");

In section "ctype (locale-aware)":

int compat_islower(int c) { return islower(c); }
__asm__(".symver compat_islower, islower@LIBC");

int compat_isxdigit(int c) { return isxdigit(c); }
__asm__(".symver compat_isxdigit, isxdigit@LIBC");

Then rebuild libs with ./NativeFix/build_compat.sh
After that demo hand scene (Assets/Samples/XR Interaction Toolkit/3.3.1/Hands Interaction Demo/HandsDemoScene.unity) is loading and pocking is working (but I still have problems with grabbing though). Tested both on Quest 3 Pro and Pico 4 ultra via AllVR.

As described in the main project, the problem is realy only with launching things in Editor, building works even without fixes.