linux-user: rename gettid() to sys_gettid() to avoid clash with glibc

The glibc-2.29.9000-6.fc31.x86_64 package finally includes the gettid()
function as part of unistd.h when __USE_GNU is defined. This clashes
with linux-user code which unconditionally defines this function name
itself.

/home/berrange/src/virt/qemu/linux-user/syscall.c:253:16: error: static declaration of ‘gettid’ follows non-static declaration
  253 | _syscall0(int, gettid)
      |                ^~~~~~
/home/berrange/src/virt/qemu/linux-user/syscall.c:184:13: note: in definition of macro ‘_syscall0’
  184 | static type name (void)   \
      |             ^~~~
In file included from /usr/include/unistd.h:1170,
                 from /home/berrange/src/virt/qemu/include/qemu/osdep.h:107,
                 from /home/berrange/src/virt/qemu/linux-user/syscall.c:20:
/usr/include/bits/unistd_ext.h:34:16: note: previous declaration of ‘gettid’ was here
   34 | extern __pid_t gettid (void) __THROW;
      |                ^~~~~~
  CC      aarch64-linux-user/linux-user/signal.o
make[1]: *** [/home/berrange/src/virt/qemu/rules.mak:69: linux-user/syscall.o] Error 1
make[1]: *** Waiting for unfinished jobs....
make: *** [Makefile:449: subdir-aarch64-linux-user] Error 2

While we could make our definition conditional and rely on glibc's impl,
this patch simply renames our definition to sys_gettid() which is a
common pattern in this file.

Signed-off-by: Daniel P. Berrangé <[email protected]>
Reviewed-by: Richard Henderson <[email protected]>
Reviewed-by: Laurent Vivier <[email protected]>
Message-Id: <[email protected]>
Signed-off-by: Laurent Vivier <[email protected]>
(cherry picked from commit 71ba74f67eaca21b0cc9d96f534ad3b9a7161400)

linux-user/syscall.c

@@ -250,7 +250,8 @@ static type name (type1 arg1,type2 arg2,type3 arg3,type4 arg4,type5 arg5,	\
 #define TARGET_NR__llseek TARGET_NR_llseek
 #endif
 
-_syscall0(int, gettid)
+#define __NR_sys_gettid __NR_gettid
+_syscall0(int, sys_gettid)
 
 /* For the 64-bit guest on 32-bit host case we must emulate
  * getdents using getdents64, because otherwise the host
@@ -6376,7 +6377,7 @@ static void *clone_func(void *arg)
     cpu = ENV_GET_CPU(env);
     thread_cpu = cpu;
     ts = (TaskState *)cpu->opaque;
-    info->tid = gettid();
+    info->tid = sys_gettid();
     task_settid(ts);
     if (info->child_tidptr)
         put_user_u32(info->tid, info->child_tidptr);
@@ -6521,9 +6522,9 @@ static int do_fork(CPUArchState *env, unsigned int flags, abi_ulong newsp,
                mapping.  We can't repeat the spinlock hack used above because
                the child process gets its own copy of the lock.  */
             if (flags & CLONE_CHILD_SETTID)
-                put_user_u32(gettid(), child_tidptr);
+                put_user_u32(sys_gettid(), child_tidptr);
             if (flags & CLONE_PARENT_SETTID)
-                put_user_u32(gettid(), parent_tidptr);
+                put_user_u32(sys_gettid(), parent_tidptr);
             ts = (TaskState *)cpu->opaque;
             if (flags & CLONE_SETTLS)
                 cpu_set_tls (env, newtls);
@@ -11795,7 +11796,7 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
         break;
 #endif
     case TARGET_NR_gettid:
-        ret = get_errno(gettid());
+        ret = get_errno(sys_gettid());
         break;
 #ifdef TARGET_NR_readahead
     case TARGET_NR_readahead: