## Description
Some AARCH64 platforms are incompatible with 64k runtime granularity.
This PR adds a build option that is consumed to enable a deprecated
option to set the runtime page allocation granularity to 4k. This option
should not be used except for old platforms that cannot be updated to
comply with 64k runtime granularity. Using this option breaks
compatibility with the UEFI spec.
For each item, place an "x" in between `[` and `]` if true. Example:
`[x]`.
_(you can also check items in the GitHub UI)_
- [x] Impacts functionality?
- **Functionality** - Does the change ultimately impact how firmware
functions?
- Examples: Add a new library, publish a new PPI, update an algorithm,
...
- [ ] Impacts security?
- **Security** - Does the change have a direct security impact on an
application,
flow, or firmware?
- Examples: Crypto algorithm change, buffer overflow fix, parameter
validation improvement, ...
- [ ] Breaking change?
- **Breaking change** - Will anyone consuming this change experience a
break
in build or boot behavior?
- Examples: Add a new library class, move a module to a different repo,
call
a function in a new library class in a pre-existing module, ...
- [ ] Includes tests?
- **Tests** - Does the change include any explicit test code?
- Examples: Unit tests, integration tests, robot tests, ...
- [ ] Includes documentation?
- **Documentation** - Does the change contain explicit documentation
additions
outside direct code modifications (and comments)?
- Examples: Update readme file, add feature readme file, link to
documentation
on an a separate Web page, ...
## How This Was Tested
Tested with setting flag and unsetting.
## Integration Instructions
Do not use this option without an old platform that cannot support 64k.
For those platforms, set the following in the platform DSC:
```c
MSFT:*_*_*_CC_FLAGS = /D __DEPRECATED_AARCH64_4K_RUNTIME_GRANULARITY
GCC:*_*_*_CC_FLAGS = -D __DEPRECATED_AARCH64_4K_RUNTIME_GRANULARITY
```
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