Easier way is to just download and use the Binary files.
This is for Ubuntu 18.04.2 LTS
1# install dependencies
2sudo apt install -y automake autoconf libssl-dev libtool python-dev
3
4# use the latest stable release
5git clone https://github.com/facebook/watchman.git --depth 1
6cd watchman
7./autogen.sh
8./configure
9make
10sudo make install