EdkCompatibilityPkg: Fixed build for AArch64

EdkCompatibilityPkg: Fixed build for AArch64

The architecture specific folders must be capitalized (first letter as
a capital letter and the remaining letters in lower case) (INF spec -
2.2.4 Naming Conventions).

The BaseTools only support this requirement for INF revision prior to
0x00010005 (mainly used by EdkCompatibilityPkg, EdkShellPkg, UEFI SCT).

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Olivier Martin <olivier.martin@arm.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@14620 6f19259b-4bc3-4df7-8a09-765794883524