Resources: Use path names for ignored dirs
Resources: Use path names for ignored dirs

### Description

Ignored directories are collected for the sake of exporters that use
a blacklist-style approach similar to these build tools. This ignore
list will include `/filer/<gibberish>` when exported from the online
Compiler. This patch fixes that behavoir.

### Pull request type

    [x] Fix
    [ ] Refactor
    [ ] Target update
    [ ] Functionality change
    [ ] Docs update
    [ ] Test update
    [ ] Breaking change

kjbracey-arm/mbed,mbedmicro/mbed,mbedmicro/mbed,kjbracey-arm/mbed,mbedmicro/mbed,andcor02/mbed-os,andcor02/mbed-os,andcor02/mbed-os,andcor02/mbed-os,mbedmicro/mbed,andcor02/mbed-os,mbedmicro/mbed,andcor02/mbed-os,kjbracey-arm/mbed,kjbracey-arm/mbed