I get the following error when trying to use gtools' -gcollapse- command:
file env_set_macosx.plugin not found
(error occurred while loading gcollapse.ado)
r(601);

Simple example re-producing the error:
. ado uninstall gtools

package gtools from https://raw.githubusercontent.com/mcaceresb/stata-gtools/master/build
^

(package uninstalled)

. net install gtools, from(https://raw.githubusercontent.com/mcaceresb/stata-gtools/master/build/)
checking gtools consistency and verifying not already installed...
installing into /Users/USER/Library/Application Support/Stata/ado/plus/...
installation complete.

. sysuse auto
(1978 Automobile Data)

. gcollapse (mean) price, by(make)
file env_set_macosx.plugin not found
(error occurred while loading gcollapse.ado)
r(601);