Manual cherrypick of Jeff Newquist's CL 17570840:
Provide API to override output format of ISPC for platforms that should use an option other than --emit-obj
#rb brian.white
Additional changes by Jeff Newquist:
- update to ISPC 1.16.1
- set CPU target for ISPC
#rb Jeff.Newquist
#lockdown michal.valient
#jira UE-124897, FROST-5511
#preflight 615659689dc4c50001387dcc
#ROBOMERGE-OWNER: jon.nabozny
#ROBOMERGE-AUTHOR: eric.mcdaniel
#ROBOMERGE-SOURCE: CL 17693756 via CL 17968371 via CL 18366221 via CL 18366330
#ROBOMERGE-BOT: STARSHIP (Release-Engine-Staging -> Release-Engine-Test) (v895-18170469)
[CL 18366391 by jon nabozny in ue5-release-engine-test branch]