init.sh: error out if .git/ is a symlink

the current behaviour is a relic from the older lbmk
design, before recent auditing.

the current logic would cause xbmk to continue execution,
going into a child process with .git/ being a symlink.

The .git/ directory should never be a symlink, because
it is extremely error-prone.

Signed-off-by: Leah Rowe <leah@libreboot.org>

include/init.sh

@@ -195,7 +195,7 @@ xbmk_git_init()
 		    || err "Run this first: $gitcmd \"your ${gitcmd##*.}\""
 	done
 
-	[ -L ".git" ] && return 1
+	[ -L ".git" ] && err "'$xbmkpwd/.git' is a symlink"
 	[ -e ".git" ] && return 0
 	eval "`setvars "$(date -Rud @$versiondate)" cdate _nogit`"