tree 24f0edddabed3831a31cb094b0cee4116456a483
parent 6c3a94c01f84eccacb0a6e060e698cfa20b79ff9
author Sebastian Bøe <sebastian.boe@nordicsemi.no> 1523897723 +0200
committer Carles Cufí <carles.cufi@nordicsemi.no> 1524823562 +0200

cmake: Find a directory that could be used to cache files

To improve the build system's "clean build" runtime we need to cache
files in a directory outside of the build directory.

Caching files outside of the build directory is is already being done
to a certain degree today. For instance, if a user has installed
ccache it will cache files in $HOME/.ccache/.

This commit locates a directory that is suitable for caching files in
a cross-platform way. For instance on Linux this is believed to be
$HOME, on Windows this is believed to be %LOCALAPPDATA%.

If for whatever reason no environment variables are are found to be
suitable we fall back to using $ZEPHYR_BASE/.cache/. For users that
often use 'git -clean' the caching mechanism will not work as well,
but it will at least be better than no caching at all.

Signed-off-by: Sebastian Bøe <sebastian.boe@nordicsemi.no>