configure.sh: Don't append the apps directory path setting if the correct...

configure.sh:  Don't append the apps directory path setting if the correct setting is already in defined in the defconfig file.

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@5101 42af7a65-404d-4744-a932-0658087f49c3