HADOOP-16263. Update BUILDING.txt with macOS native build instructions. Contributed by Siyao Meng.
HADOOP-16263. Update BUILDING.txt with macOS native build instructions. Contributed by Siyao Meng.

Signed-off-by: Wei-Chiu Chuang <69b92d7faa6f3821f81872c17428713be71a6bb0@apache.org>

nandakumar131/hadoop,wwjiang007/hadoop,apurtell/hadoop,apache/hadoop,nandakumar131/hadoop,mapr/hadoop-common,mapr/hadoop-common,apurtell/hadoop,wwjiang007/hadoop,lukmajercak/hadoop,apache/hadoop,JingchengDu/hadoop,apache/hadoop,nandakumar131/hadoop,JingchengDu/hadoop,steveloughran/hadoop,wwjiang007/hadoop,nandakumar131/hadoop,plusplusjiajia/hadoop,plusplusjiajia/hadoop,lukmajercak/hadoop,lukmajercak/hadoop,mapr/hadoop-common,apurtell/hadoop,nandakumar131/hadoop,mapr/hadoop-common,plusplusjiajia/hadoop,lukmajercak/hadoop,nandakumar131/hadoop,mapr/hadoop-common,plusplusjiajia/hadoop,apache/hadoop,steveloughran/hadoop,JingchengDu/hadoop,apurtell/hadoop,apache/hadoop,steveloughran/hadoop,JingchengDu/hadoop,steveloughran/hadoop,wwjiang007/hadoop,nandakumar131/hadoop,apache/hadoop,lukmajercak/hadoop,JingchengDu/hadoop,apurtell/hadoop,JingchengDu/hadoop,lukmajercak/hadoop,apache/hadoop,steveloughran/hadoop,JingchengDu/hadoop,lukmajercak/hadoop,wwjiang007/hadoop,steveloughran/hadoop,mapr/hadoop-common,wwjiang007/hadoop,plusplusjiajia/hadoop,apurtell/hadoop,apurtell/hadoop,plusplusjiajia/hadoop,wwjiang007/hadoop,steveloughran/hadoop,mapr/hadoop-common,plusplusjiajia/hadoop