How to modify environment variables passed to custom CMake target?

Question

Perhaps I am missing something obvious, but I can't seem to figure out how to explicitly set environment variables that can be seen by processes launched through add_custom_target().

I tried the following:

set(ENV{PATH} "C:/Some/Path;$ENV{PATH}")
add_custom_target(newtarget somecommand)

Unfortunately, the %PATH% environment variable appears unchanged to somecommand. (I have set up a Gist that reproduces the problem here.)

What am I doing wrong?

Answer 1

A portable way of setting environment variables for a custom target is to use CMake's command-line tool mode command env:

env [--unset=NAME]... [NAME=VALUE]... COMMAND [ARG]...

Run command in a modified environment.

E.g.:

add_custom_target(newtarget ${CMAKE_COMMAND} -E env NAME=VALUE somecommand)

Also see Command Line Tool Mode.