Add a makefile for cleaning the kernels code.

Makefile

@@ -0,0 +1,12 @@
+clean-ptx:
+	find target -name "*.ptx" -type f -delete
+	echo "" > kernels/src/lib.rs
+	touch kernels/build.rs
+
+clean:
+	cargo clean
+
+test:
+	cargo test
+
+all: test