Fix style issues in IAR exporter

[theotherjimmy]

Some of this stuff began to bother me, so I fixed it.

[0xc0170]

LGTM

This does not change it, just for future that in our codebase: tgt vs target , we shall use full name for readability (of course if its not 50 characters long)

[0xc0170]

Travis failure

0.23s$ python tools/project.py -S
Traceback (most recent call last):
  File "tools/project.py", line 15, in <module>
    from tools.export import EXPORTERS, mcu_ide_matrix, mcu_ide_list, export_project, get_exporter_toolchain
  File "/home/travis/build/ARMmbed/mbed-os/tools/export/__init__.py", line 31, in <module>
    from tools.export import lpcxpresso, ds5_5, iar, makefile
  File "/home/travis/build/ARMmbed/mbed-os/tools/export/iar/__init__.py", line 17, in <module>
    class IAR(Exporter):
  File "/home/travis/build/ARMmbed/mbed-os/tools/export/iar/__init__.py", line 33, in IAR
    _iar_support(obj, IAR_DEFS.keys())]
NameError: name '_iar_support' is not defined
``

[theotherjimmy]

Huh.

[theotherjimmy]

This does not change it, just for future that in our codebase: tgt vs target , we shall use full name for readability (of course if its not 50 characters long)

No we "shall" not. target can be a function name. If it is, don't create a local variable that shadows it.

[adbridge]

/morph export-build

[mbed-bot]

Result: SUCCESS

Your command has finished executing! Here's what you wrote!

/morph export-build

Output

mbed Build Number: 74

All exports and builds passed!

[theotherjimmy]

@0xc0170 and I discussed variable naming offline, and came to the conclusion that tgt and target are both bad, and neither should be used. The word "target" is overloaded like it's going out of style in this codebase, so we should avoid confusion by being more specific. I opted for mcu here.