Tools: Fix incrimental compile dep tracking

[theotherjimmy]

Description

I recently introduced a general purpose function for creating command files.
This function used the hash in naming the file, but not in checking for
updates. This PR corrects the incrimental compile behavior of links.

In the process, I noticed that mbed_config.h changes every compile under
python 3. I'll be correcting that shortly. That should be resolved now

TODO

• Fix incrimental flags for linker
• Fix Python 3 mbed_config.h orering

Pull request type

[x] Fix
[ ] Refactor
[ ] New target
[ ] Feature
[ ] Breaking change

[cmonr]

Interesting to know that Py3 doesn't sort by default.

/morph build

[mbed-ci]

Build : SUCCESS

Build number : 2712
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/7646/

Triggering tests

/morph test
/morph uvisor-test
/morph export-build
/morph mbed2-build

[mbed-ci]

Exporter Build : SUCCESS

Build number : 2341
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/exporter/7646/

[mbed-ci]

Test : FAILURE

Build number : 2443
Test logs :http://mbed-os-logs.s3-website-us-west-1.amazonaws.com/?prefix=logs/7646/2443

[0xc0170]

/morph test

[mbed-ci]

Test : SUCCESS

Build number : 2447
Test logs :http://mbed-os-logs.s3-website-us-west-1.amazonaws.com/?prefix=logs/7646/2447