Always use config.mk in make install instructions

docs/install/c_plus_plus.md

@@ -6,7 +6,11 @@ To enable C++ package, just add `USE_CPP_PACKAGE=1` in the [build from source](b
 For example to build MXNet with GPU support and the C++ package, OpenCV, and OpenBLAS, from the project root you would run:
 
 ```bash
-make -j USE_CPP_PACKAGE=1 USE_OPENCV=1 USE_BLAS=openblas USE_CUDA=1
+echo "USE_CPP_PACKAGE=1" >> ./config.mk
+echo "USE_OPENCV=1" >> ./config.mk
+echo "USE_BLAS=openblas" >> ./config.mk
+echo "USE_CUDA=1" >> ./config.mk
+make -j $(nproc)
 ```
 
 You may also want to add the MXNet shared library to your `LD_LIBRARY_PATH`:

docs/install/osx_setup.md

@@ -96,7 +96,14 @@ The file called ```osx.mk``` has the configuration required for building MXNet o
 To build with MKLDNN
 
 ```bash
-LIBRARY_PATH=$(brew --prefix llvm)/lib/ make -j $(sysctl -n hw.ncpu) CC=$(brew --prefix llvm)/bin/clang++ CXX=$(brew --prefix llvm)/bin/clang++ USE_OPENCV=1 USE_OPENMP=1 USE_MKLDNN=1 USE_BLAS=apple USE_PROFILER=1
+echo "CC=$(brew --prefix llvm)/bin/clang++" >> ./config.mk
+echo "CXX=$(brew --prefix llvm)/bin/clang++" >> ./config.mk
+echo "USE_OPENCV=1" >> ./config.mk
+echo "USE_OPENMP=1" >> ./config.mk
+echo "USE_MKLDNN=1" >> ./config.mk
+echo "USE_BLAS=apple" >> ./config.mk
+echo "USE_PROFILER=1" >> ./config.mk
+LIBRARY_PATH=$(brew --prefix llvm)/lib/ make -j $(sysctl -n hw.ncpu)
 ```
 
 If building with ```GPU``` support, add the following configuration to config.mk and build:

docs/install/ubuntu_setup.md

@@ -163,23 +163,33 @@ If building on CPU and using OpenBLAS:
 ```bash
     git clone --recursive https://github.com/apache/incubator-mxnet.git
     cd incubator-mxnet
-    make -j $(nproc) USE_OPENCV=1 USE_BLAS=openblas
+    echo "USE_OPENCV = 1" >> ./config.mk
+    echo "USE_BLAS = openblas" >> ./config.mk
+    make -j $(nproc)
 ```
 
 If building on CPU and using MKL and MKL-DNN (make sure MKL is installed according to [Math Library Selection](build_from_source.html#math-library-selection) and [MKL-DNN README](https://github.com/apache/incubator-mxnet/blob/master/MKLDNN_README.md)):
 
 ```bash
     git clone --recursive https://github.com/apache/incubator-mxnet.git
     cd incubator-mxnet
-    make -j $(nproc) USE_OPENCV=1 USE_BLAS=mkl USE_MKLDNN=1
+    echo "USE_OPENCV = 1" >> ./config.mk
+    echo "USE_BLAS = openblas" >> ./config.mk
+    echo "USE_MKLDNN = 1" >> ./config.mk
+    make -j $(nproc)
 ```
 
 If building on GPU and you want OpenCV and OpenBLAS (make sure you have installed the [CUDA dependencies first](#cuda-dependencies)):
 
 ```bash
     git clone --recursive https://github.com/apache/incubator-mxnet.git
     cd incubator-mxnet
-    make -j $(nproc) USE_OPENCV=1 USE_BLAS=openblas USE_CUDA=1 USE_CUDA_PATH=/usr/local/cuda USE_CUDNN=1
+    echo "USE_OPENCV = 1" >> ./config.mk
+    echo "USE_BLAS = openblas" >> ./config.mk
+    echo "USE_CUDA = 1" >> ./config.mk
+    echo "USE_CUDA_PATH = /usr/local/cuda" >> ./config.mk
+    echo "USE_CUDNN = 1" >> ./config.mk
+    make -j $(nproc)
 ```
 
 *Note* - USE_OPENCV and USE_BLAS are make file flags to set compilation options to use OpenCV and BLAS library. You can explore and use more compilation options in `make/config.mk` and also review common [usage examples](build_from_source.html#usage-examples).
@@ -348,7 +358,9 @@ $ sudo apt-get install -y libopencv-dev
 ```bash
 $ git clone --recursive https://github.com/apache/incubator-mxnet
 $ cd incubator-mxnet
-$ make -j $(nproc) USE_OPENCV=1 USE_BLAS=openblas
+$ echo "USE_OPENCV = 1" >> ./config.mk
+$ echo "USE_BLAS = openblas" >> ./config.mk
+$ make -j $(nproc)
 ```
 
 *Note* - USE_OPENCV and USE_BLAS are make file flags to set compilation options to use OpenCV and BLAS library. You can explore and use more compilation options in `make/config.mk`.