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>

scons/gallium.py

@@ -381,6 +381,9 @@ def generate(env):
         if check_header(env, 'sys/shm.h'):
             cppdefines += ['HAVE_SYS_SHM_H']
 
+        if check_functions(env, ['strtok_r']):
+            cppdefines += ['HAVE_STRTOK_R']
+
         #FIXME: we should really be checking for the major()/minor()
         # functions/macros in these headers, but check_functions()'s
         # SConf.CheckFunc() doesn't seem to support macros.