testsuite: make use of config.interp_force_dyn

This commit takes config.interp_force_dyn into consideration when
setting up TH/ghci way flags.

(cherry picked from commit 93b8af80)

testsuite/config/ghc

@@ -282,7 +282,7 @@ def get_compiler_info():
         ghc_env['HAVE_PROFILING'] = 'YES'
 
     # See Note [WayFlags]
-    if config.ghc_dynamic:
+    if config.interp_force_dyn or config.ghc_dynamic:
         config.ghc_th_way_flags = "-dynamic"
         config.ghci_way_flags   = "-dynamic"
         config.plugin_way_flags = "-dynamic"