Fix #1256, add rtems 6 support

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Checklist (Please check before submitting)

• I reviewed the Contributing Guide.
• I signed and emailed the appropriate Contributor License Agreement to [email protected] and copied [email protected].

Describe the contribution

• Fix Add OSAL support for RTEMS 6 #1256

These changes add support for RTEMS 6 in the RTEMS OSAL and pc-rtems OSAL BSP. The changes consist of modifications to the conditional compilation blocks and a couple of new conditional compilation blocks in the pc-rtems OSAL BSP startup code to account for an include and API that was deprecated in RTEMS 6.
In the RTEMS OSAL, the existing conditional compilation blocks were flipped from:

if RTEMS 5
   RTEMS 5 specific statement(s)
else
   RTEMS 4.11 specific statement(s)
endif

to:

if RTEMS 4.11
   RTEMS 4.11 specific statement(s)
else
   RTEMS 5 and above specific statement(s)
endif

By flipping the blocks as described above, it should work with future versions of RTEMS provided the API does not change.

There is also a change in the os-impl-loader.c file to solve a warning with GCC 12. GCC 12 is now used by RTEMS 6.

Testing performed
All tests were run on the QEMU RTEMS 4.11, QEMU RTEMS 5, and the new QEMU RTEMS 6 containers.

Expected behavior changes
There should be no impact to the behavior. All tests passed on RTEMS 4.11, 5, and 6.

System(s) tested on
QEMU x86 with pc-rtems RTEMS BSP and cFS pc-rtems platform. In addition these changes are being used on a generic-rtems platform that will be submitted in a future PR.

Additional context
This is the last set of code changes in the first round of RTEMS 6 updates described here:
nasa/cFS#468

Third party code
None

Contributor Info - All information REQUIRED for consideration of pull request
Alan Cudmore, NASA/GSFC Code 582.0

[astrogeco]

CCB:2022-05-25 APPROVED

• Eventually deprecate RTEMS 4.11 CI testing