IOTCORE-389 - bring back legacy alignment for Arm C6

[JanneKiiskila]

Description

Quite a few of the scatter files are not (yet) aligned to 8-byte
boundaries and therefore the removal of legacy alignment feature
(which is under deprecation warning, but it actually not YET
deprecated) broke quite a few builds to this error:

Error: L6244E: Exec region RW_IRAM1 address (0x200001ac) not aligned on a 8 byte boundary.

We must bring this option now back to fix the builds.

This option to ld (--legacyalign) can only be removed once all of
the scatter files have been fixed.

Pull request type

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

[JanneKiiskila]

@0xc0170 @adbridge @kjbracey-arm - this needs to get in ASAP, please. To next Mbed OS 5.10 RC.

[cmonr]

@JanneKiiskila In the future, you can simply use @ARMmbed/mbed-os-maintainers as a shorthand.

/morph build

[mbed-ci]

Build : SUCCESS

Build number : 3018
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/8012/

Triggering tests

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

[mbed-ci]

Exporter Build : FAILURE

Build number : 2630
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/exporter/8012/

[mbed-ci]

Test : SUCCESS

Build number : 2784
Test logs :http://mbed-os-logs.s3-website-us-west-1.amazonaws.com/?prefix=logs/8012/2784

[0xc0170]

/morph export-build

[c1728p9]

Thanks for the fix @JanneKiiskila. @cmonr and @studavekar can we expand ARMC6 CI testing to build all boards so we can catch regressions like this?

[mbed-ci]

Exporter Build : SUCCESS

Build number : 2632
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/exporter/8012/

[JanneKiiskila]

Thanks.

[andrewc-arm]

Hi,
I weaved through the code and finally found this issue while I am trying to solve this issue from my partner.
My research showed that legacyalign removes the padding to reduce more space.
http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0803g/pge1362075504330.html

Using --legacyalign, the linker assumes execution regions and load regions to be four-byte aligned. This option enables the linker to minimize the amount of padding that it inserts into the image.

But this issue is saying that there is a misalignment and we want to reduce padding via adding legacyalign. Does it make sense? I thought it should be other way around isn't it?