tools: install.fish: Modify method to get base directory.

Current method assumes that you are in the esp-idf directory when executing install. This method will get the correct path regardless of where you execute from.

Merges https://github.com/espressif/esp-idf/pull/6718

install.fish

@@ -1,6 +1,6 @@
 #!/usr/bin/env fish
 
-set basedir $PWD
+set basedir (realpath (dirname (status -f)))
 
 set -x IDF_PATH $basedir