build: Don't auto-compile tests.

* Makefile.am (TESTS_ENVIRONMENT): Add `--no-auto-compile'.

Makefile.am

@@ -47,7 +47,7 @@ TESTS =						\
 TESTS_ENVIRONMENT =							\
   NIXPKGS="$(NIXPKGS)"							\
   GUILE_LOAD_COMPILED_PATH="$(top_builddir):$$GUILE_LOAD_COMPILED_PATH"	\
-  $(GUILE) -L "$(top_srcdir)"
+  $(GUILE) --no-auto-compile -L "$(top_srcdir)"
 
 EXTRA_DIST = build-aux/config.rpath $(TESTS)
 CLEANFILES = $(GOBJECTS) *.log