Improve Jenkins tests

Dockerfile.jenkins

@@ -1,4 +1,4 @@
 FROM schemers/chibi:head
 RUN apt-get update && apt-get install -y \
-    gcc ca-certificates libffi-dev docker.io
+    gcc ca-certificates libffi-dev docker.io make
 RUN snow-chibi install --impls=chibi retropikzel.test-r7rs

Makefile

@@ -56,6 +56,7 @@ testfiles: ${PKG}
 
 test: testfiles
 	cd ${tmpdir} && \
+		COMPILE_R7RS_DEBUG=1 \
 		COMPILE_R7RS=${SCHEME} \
 		CSC_OPTIONS="${CSC_OPTIONS}" \
 		compile-r7rs ${LIB_PATHS} -o test-program test.${SFX}