Compile Mode and "host" Emacs

[Sebastian Wiesner]

Hello,

how can a compilation process obtain the path to the Emacs executable
which started it?

I know that Emacs sets $EMACS and $INSIDE_EMACS in the environment of
compile processes, but the values of these variables aren't exactly
helpful and I didn't see any other environment variables in the
compile code.  So apparently environment variables can't help me.

Is there any way to find out the path to the "host" Emacs executable?
Preferably with not too much trickery?

Sincerely,
Sebastian Wiesner