Add nnvm target to Makefile (#1245)

Makefile

@@ -256,6 +256,8 @@ all: ${BUILD_TARGETS}
 runtime: lib/libtvm_runtime.$(SHARED_LIBRARY_SUFFIX)
 web: lib/libtvm_web_runtime.js lib/libtvm_web_runtime.bc
 topi: lib/libtvm_topi.$(SHARED_LIBRARY_SUFFIX)
+nnvm:
+	$(MAKE) -C nnvm
 
 
 include tests/cpp/unittest.mk
@@ -387,6 +389,7 @@ jvminstall:
 clean:
 	$(RM) -rf build lib bin *~ */*~ */*/*~ */*/*/*~ */*.o */*/*.o */*/*/*.o */*.d */*/*.d */*/*/*.d
 	cd HalideIR; make clean; cd $(ROOTDIR)
+	$(MAKE) -C nnvm clean
 
 -include build/*.d
 -include build/*/*.d

docs/install/index.rst

@@ -67,12 +67,11 @@ We can then build tvm by `make`.
 
   make -j4
 
-After we build tvm, we can proceed to build nnvm using the following script.
+After we build tvm, we can proceed to build nnvm using the following command.
 
 .. code:: bash
 
-  cd nnvm
-  make -j4
+  make nnvm -j4
 
 
 This will creates `libnnvm_compiler.so` under the `nnvm/lib` folder.