install: Use readlink -f rather than realpath.

It does exactly the same thing, though the name is less transparent; and
it simplifies the script by avoiding an extra, early `apt-get install`.

scripts/lib/install

@@ -68,6 +68,8 @@ fi
 # Do set -x after option parsing is complete
 set -x
 
+ZULIP_PATH="$(readlink -f $(dirname $0)/../..)"
+
 # Force a known locale.  Some packages on PyPI fail to install in some locales.
 export LC_ALL="en_US.UTF-8"
 
@@ -80,13 +82,6 @@ if [ "$mem_kb" -lt 1900000 ]; then
     exit 1
 fi
 
-if ! [ -e /usr/bin/realpath ]; then
-    # realpath is in coreutils on Xenial, but not in Trusty
-    apt-get install -y realpath
-fi
-
-ZULIP_PATH="$(realpath $(dirname $0)/../..)"
-
 # setup-apt-repo does an `apt-get update`
 "$ZULIP_PATH"/scripts/lib/setup-apt-repo
 

tools/test-install/prepare-base

@@ -44,7 +44,7 @@ run apt-get update
 # As an optimization, we install a bunch of packages the installer
 # would install for itself.
 run apt-get install -y --no-install-recommends \
-  xvfb parallel netcat unzip zip jq python3-pip wget curl realpath eatmydata \
+  xvfb parallel netcat unzip zip jq python3-pip wget curl eatmydata \
   git crudini openssl ssl-cert \
   build-essential python3-dev \
   closure-compiler memcached rabbitmq-server redis-server \