[TargetParser][clang] Parse Intel IGCA targets from --offload-arch into OffloadArch (#227468)
Add support for Intel IGCA targets, such as igca_20ca, in
--offload-arch.
Clang now parses an IGCA target from the --offload-arch value and stores
it as an OffloadArch.
This code will be used later in clang in both the driver and the
frontend to enable clang support for compiling SYCL programs with
support for specific IGCA targets.
Assisted-by: Claude code (+ some Github copilot)
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Co-authored-by: Tom Honermann <tom@honermann.net>
Co-authored-by: srividya sundaram <srividya.sundaram@intel.com>