Make implicit func declarations an error in tests

Author: manorom

clang/tools/sotoc/test/lit.cfg

@@ -35,9 +35,9 @@ config.test_format = lit.formats.ShTest()
 
 config.test_flags = '-I ' + config.test_source_root + ' ' + \
                     '-I ' + config.omp_header_directory + ' ' + \
-                    '-fopenmp ' #+ \
-                    #'-Xopenmp-target \"-Xlinker -fopenmp-static\" ' #+ \
-                    #'-Werror=implicit-function-declaration'
+                    '-fopenmp ' + \
+                    '-Werror=implicit-function-declaration '
+                    #'-Xopenmp-target \"-Xlinker -fopenmp-static\" '
 
 # Setup environment to find dynamic library at runtime
 append_dynamic_library_path(config.library_dir)