patch 8.1.0003: the :compiler command is not tested

Problem:    The :compiler command is not tested.
Solution:   Add a test. (Dominique Pelle, closes #2930)
diff --git a/src/Makefile b/src/Makefile
index 98fd142..0e4c555 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -2150,6 +2150,7 @@
 	test_cmdline \
 	test_command_count \
 	test_comparators \
+	test_compiler \
 	test_crypt \
 	test_cscope \
 	test_cursor_func \