On Fedora rawhide we get the following build failure:

    In file included from shared/systemd/src/basic/alloc-util.c:3:
    ./shared/systemd/sd-adapt-shared/nm-sd-adapt-shared.h:114:21: error: static declaration of 'gettid' follows non-static declaration
      114 | static inline pid_t gettid(void) {
          |                     ^~~~~~
    In file included from /usr/include/unistd.h:1170,
                     from /usr/include/glib-2.0/gio/gcredentials.h:32,
                     from /usr/include/glib-2.0/gio/gio.h:46,
                     from ./shared/nm-utils/nm-macros-internal.h:31,
                     from ./shared/nm-default.h:293,
                     from ./shared/systemd/sd-adapt-shared/nm-sd-adapt-shared.h:22,
                     from shared/systemd/src/basic/alloc-util.c:3:
    /usr/include/bits/unistd_ext.h:34:16: note: previous declaration of 'gettid' was here
       34 | extern __pid_t gettid (void) __THROW;
          |                ^~~~~~

glibc supports now gettid() call ([1]) which conflicts with our compat
implementation. Rename it.

[1] https://sourceware.org/git/?p=glibc.git;a=commit;h=1d0fc213824eaa2a8f8c4385daaa698ee8fb7c92

(cherry picked from commit 10276322)