testsuite: Introduce threaded2_sanity way

Incredibly, we previously did not have a single way which would test the
threaded RTS with multiple capabilities and the sanity-checker enabled.

testsuite/config/ghc

@@ -22,7 +22,7 @@ config.other_ways         = ['hpc',
                              'prof_hc_hb','prof_hb',
                              'prof_hd','prof_hy','prof_hr',
                              'sanity',
-                             'threaded1_ls', 'threaded2_hT', 'debug_numa',
+                             'threaded1_ls', 'threaded2_hT', 'threaded2_sanity', 'debug_numa',
                              'llvm', 'debugllvm',
                              'profllvm', 'profoptllvm', 'profthreadedllvm',
                              'debug',
@@ -99,6 +99,7 @@ config.way_flags = {
     'threaded1_ls' : ['-threaded', '-debug'],
     'threaded2'    : ['-O', '-threaded'],
     'threaded2_hT' : ['-O', '-threaded'],
+    'threaded2_sanity': ['-O', '-threaded', '-debug'],
     'hpc'          : ['-O', '-fhpc'],
     'prof_hc_hb'   : ['-O', '-prof', '-static', '-fprof-auto'],
     'prof_hb'      : ['-O', '-prof', '-static', '-fprof-auto'],
@@ -144,6 +145,7 @@ config.way_rts_flags = {
     'threaded1_ls' : ['-ls'],
     'threaded2'    : ['-N2', '-ls'],
     'threaded2_hT' : ['-N2', '-hT'],
+    'threaded2_sanity' : ['-N2', '-DS'],
     'hpc'          : [],
     'prof_hc_hb'   : ['-hc', '-hbvoid'],
     'prof_hb'      : ['-hb'],