Multiple LDC installations

[Marco Leise]

I would like to get multiple system installations of LDC
working on Gentoo, by renaming binaries and paths. I've got
that working for DMD, but I can't get my head around CMake. I
thought I could just append the version (0.12.0) to the
LDC_EXE_NAME, but that broke the build process with make -j3.
And otherwise it seems to use the installed /usr/bin/ldc2 as a
fallback in the build phase which should not happen at all.

So I'd appreciate if someone could help be out with this.
I've never used CMake before.

-- 
Marco