Export, Embitz: Avoid assigning self.resources.linker_script

[theotherjimmy]

Description

At some point in the past, self.linker_script was changed from
"assignable" to not allowing assignment. This PR changes the Embitz
exporter to avoid assigning this variable, and therefore fixes the
exporter. This change also simplifies the expoter code

Pull request type

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

[cmonr]

/morph build

[mbed-ci]

Build : FAILURE

Build number : 3016
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/7939/

[cmonr]

Strange that this temp file error is starting to show up...

ToolException: Fatal error: A1023E: File "/tmp/file44uSrI" could not be opened: No such file or directory

/morph build

[cmonr]

@ARMmbed/mbed-os-test ^^^

[mbed-ci]

Build : SUCCESS

Build number : 3019
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/7939/

Triggering tests

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

[mbed-ci]

Exporter Build : FAILURE

Build number : 2631
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/exporter/7939/

[mbed-ci]

Test : SUCCESS

Build number : 2785
Test logs :http://mbed-os-logs.s3-website-us-west-1.amazonaws.com/?prefix=logs/7939/2785

[0xc0170]

License server problem

cc @OPpuolitaival

/morph export-build

[mbed-ci]

Exporter Build : FAILURE

Build number : 2634
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/exporter/7939/

[cmonr]

/morph export-build

[cmonr]

Another ARM network license issue.
Fyi @ARMmbed/mbed-os-test

[mbed-ci]

Exporter Build : SUCCESS

Build number : 2638
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/exporter/7939/