Update build.sh

build.sh

@@ -1,4 +1,6 @@
 #!/bin/bash
+# this is a simple scrip to make xgboost in MAC nad Linux
+# basically, it first try to make with OpenMP, if fails, disable OpenMP and make again
 if make; then
     echo "Successfully build multi-thread xgboost"
 else
@@ -8,4 +10,4 @@ else
     make clean
     make no_omp=1
     echo "Successfully build single-thread xgboost"
-fi
+fi