Git-ignore CMakeUserPresets.json (pytorch#21715)

CMakeUserPresets.json is intended for developer- and machine-specific
configuration, such as local paths, toolchains, and IDE settings. Keep
shared project configuration in CMakePresets.json and exclude
user-specific presets from version control.

cc @digantdesai @freddan80 @per @zingo @oscarandersson8218 @mansnils
@Sebastian-Larsson @robell @rascani

Signed-off-by: Erik Lundell <erik.lundell@arm.com>

Author: Erik-Lundell

.gitignore

@@ -84,6 +84,7 @@ xcuserdata/
 /src/executorch/share/
 /src/executorch/version.py
 *_etdump
+CMakeUserPresets.json
 
 # Android
 *.aar