Bug 572799 - Replace arm64 with aarch64

Replace occurrences of arm64 with aarch64 in fragment and arch name.

build.sh changes:
Use -arch arm64 for building as aarch64 gives invalid arch name error,
set DEFAULT_OS_ARCH to aarch64

Change-Id: Ie724754dba974e157031682cac25f9f2c833b286
Reviewed-on: https://git.eclipse.org/r/c/equinox/rt.equinox.framework/+/179845
Tested-by: Thomas Watson <tjwatson@us.ibm.com>
Reviewed-by: Thomas Watson <tjwatson@us.ibm.com>
22 files changed