NSIS: using environment variable at compile time?

Question

If I'm not mistaken, all discussion about environment variables (EVs) in NSIS docs (eg ReadEnvStr), deal with EVs in the target computer: all happens at install time.

I wonder if there is any support for accesing EVs on the developer (build) machine, at compile time. Specifically, suppose I have

!define SRCDIR "C:\progs\version1\src"

...
File /r "${SRCDIR}\*.*" 

and I'd rather want to write

!define SRCDIR "%{PROG_DIR}\src"

(or something similar), where PROG_DIR is an environment variable. Can this be done?

Answer 1

!echo "$%temp%"

I'm pretty sure this is documented somewhere.