THRIFT-3718 Reduce size of docker image for build environment

This closes #931
diff --git a/build/docker/scripts/cmake.sh b/build/docker/scripts/cmake.sh
index 21b7fc6..26ccb10 100755
--- a/build/docker/scripts/cmake.sh
+++ b/build/docker/scripts/cmake.sh
@@ -1,14 +1,22 @@
 #!/bin/sh
 set -ev
 
+CMAKE_FLAGS=$*
+MAKEPROG=make
+
+if ninja --version  >/dev/null 2>&1; then
+  MAKEPROG=ninja
+  CMAKE_FLAGS="-GNinja $CMAKE_FLAGS"
+fi
+
 mkdir -p cmake_build && cd cmake_build
-cmake $* ..
+cmake $CMAKE_FLAGS ..
 for LIB in $BUILD_LIBS; do
   if ! grep "^BUILD_${LIB}:BOOL=ON$" CMakeCache.txt ; then
     echo "failed to configure $LIB"
     exit 1
   fi
 done
-make -j3
+$MAKEPROG -j3
 cpack
 ctest -VV -E "(concurrency_test|processor_test)"