[feature/native-comp] AOT eln files ignored if run from build tree

[Andy Moreton]

Hi,

I have built emacs native-comp branch for 64bit Mingw64 with
NATIVE_FULL_AOT=1 (out of tree, so build dir != source dir).

I notice that if I run the built emacs from the build dir then the
prebuilt .eln files are ignored, and async compilation of the .eln file
happens again to add them to the user eln-cache dir.

The prebuilt .eln files are not found in the user eln-cache (expected)
or the installed emacs directory (also expected), but it looks like it
does not also check the build dir (relative to the running emacs rather
than relative to the install prefix).

Running from the build dir without installing is common for developers
building from source, so it would be useful to keep this working with
native AOT builds.

    AndyM