Removes ninja for gporca

README.linux.md

-1. ORCA requires [CMake](https://cmake.org) and
-   [Ninja](https://ninja-build.org/), make sure you have them installed.
-   Installation instructions vary, please check the CMake and Ninja websites.
+1. ORCA require [CMake](https://cmake.org), make sure you have it installed.
+   Installation instructions vary, please check the CMake website.
    
 1. Install needed python modules
 

README.macOS.bash

@@ -10,7 +10,6 @@ fi
 brew install bash-completion
 brew install conan
 brew install cmake # gporca
-brew install ninja # gporca
 brew install libyaml   # enables `--enable-mapreduce`
 brew install libevent # gpfdist
 brew install apr # gpperfmon

README.md

@@ -66,8 +66,9 @@ building, see the README at the following repositories:
     git clone https://github.com/greenplum-db/gporca
     mkdir gporca/build
     cd gporca/build
-    cmake -GNinja ..
-    ninja install
+    cmake ../
+    make
+    make install
     cd ../..
     ```
     **Note**: Get the latest ORCA `git pull --ff-only` if you see an error message like below: