clean_build: try cmake3 before cmake

clean_build

@@ -3,6 +3,10 @@ cd "$(dirname $0)" || exit 1
 rm -rf build
 mkdir build || exit 1
 cd build || exit 1
-cmake -D CMAKE_BUILD_TYPE=Debug .. || exit 1
+# some environments have cmake v2 as 'cmake' and v3 as 'cmake3'
+# check for cmake3 first then fallback to just cmake
+CMAKE=`which cmake3 2>/dev/null`
+[ $? -ne 0 -o "x$CMAKE" = "x" ] && CMAKE=cmake
+$CMAKE -D CMAKE_BUILD_TYPE=Debug .. || exit 1
 make || exit 1
 echo "Build completed successfully"