mesa/imports: let the build system detect strtok_r()

Closes: https://gitlab.freedesktop.org/mesa/mesa/issues/2013
Signed-off-by: Eric Engestrom <eric.engestrom@intel.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>
Tested-by: Prodea Alexandru-Liviu <liviuprodea@yahoo.com>
Reviewed-by: Dylan Baker <dylan@pnwbakers.com>

meson.build

@@ -1149,7 +1149,7 @@ foreach h : ['xlocale.h', 'sys/sysctl.h', 'linux/futex.h', 'endian.h', 'dlfcn.h'
   endif
 endforeach
 
-foreach f : ['strtof', 'mkostemp', 'timespec_get', 'memfd_create', 'random_r', 'flock']
+foreach f : ['strtof', 'mkostemp', 'timespec_get', 'memfd_create', 'random_r', 'flock', 'strtok_r']
   if cc.has_function(f)
     pre_args += '-DHAVE_@0@'.format(f.to_upper())
   endif