uhd: paths: Harmonize around XDG Base Directory specification

Up until now, we completely ignore the XDG specification.

This commit does the following to change that:

- It uses XDG_DATA_HOME and XDG_CONFIG_HOME for cal and config data,
  respectively.
- If config data is in ~/.uhd/uhd.conf, that is still accepted, but if
  it conflicts with $XDG_CONFIG_HOME/uhd.conf, it is ignored and a
  warning is displayed
- The default location for cal data is thus ${HOME}/.local/share/uhd/cal
  on Unix, and %LOCALAPPDATA%\uhd\cal on Windows. This is a change in
  location!
- The UHD_CONFIG_DIR environment variable was confusingly named and is
  now removed. It provided an alternative location than the home
  directory. The same purpose is now much better served by XDG_DATA_HOME
  and XDG_CONFIG_HOME.

The specification can be found here:
specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html

1 files changed, 2 insertions, 2 deletions

diff --git a/host/CMakeLists.txt b/host/CMakeLists.txt
index 95f110e9e..2d966fd22 100644
--- a/host/CMakeLists.txt
+++ b/host/CMakeLists.txt
@@ -130,9 +130,9 @@ set(PKG_MAN_DIR share/man/man1)
 # UHD config files
 ########################################################################
 set(UHD_USER_CONF_FILE
-    ".uhd/uhd.conf"
+    "uhd.conf"
     CACHE STRING
-    "Location of the user-specific UHD configuration file, relative to APPDATA (or HOME)"
+    "Location of the user-specific UHD configuration file, relative to APPDATA (or XDG_CONFIG_HOME)"
 )
 if(UNIX)
     set(UHD_SYS_CONF_FILE