[FIX][SHELL] Inherit keychain's ssh-agent from env

I also use this opportunity to make it use a different directory, to
avoid polluting my $HOME.

shell/.profile

@@ -45,6 +45,9 @@ if { [ -n "$BASH_VERSION" ] && shopt -q login_shell; } ||
 
     # Use this path for `remind` calendar
     export DOTREMINDERS="$HOME/.config/remind/reminders.rem"
+
+    # Use my ssh-agent service's socket
+    export SSH_AUTH_SOCK="$XDG_RUNTIME_DIR/ssh-agent.socket"
 elif { [ -n "$BASH_VERSION" ] || [ -n "$ZSH_VERSION" ] ; } &&
     [[ $- == *i* ]]; then # When interactive, deactivate terminal freezes
     stty -ixon
@@ -54,7 +57,7 @@ fi
 unset SSH_ASKPASS
 
 # Use keychain to handle ssh-agent, in interactive shell too
-eval "$(keychain --eval id_rsa --eval shared_rsa --quiet)"
+eval "$(keychain --dir ~/.cache/keychain --inherit any-once --eval id_rsa --eval shared_rsa --quiet)"
 
 # Use my localrc script to automatically source/unsource local configurations
 source ~/.scripts/localrc