arcle.h is missing in ARC GNU tools since version 2022.03

[abrodkin]

We used to add a convenience header in the ARC GNU tools (through GCC source tree, see foss-for-synopsys-dwc-arc-processors/gcc@c1e04c1) which simplified porting of software from MWDT toolchain to GNU with mapping of MWDT intrinsics to primitives usable in GNU tools.
See https://foss-for-synopsys-dwc-arc-processors.github.io/documentation/2024.06/toolchain/advanced/intrinsics/.
For some reason since GCC 2022.03 we no longer have that header in GCC, thus it's not available in prebuilt ARC GNU tools.
I guess it might be useful so we may consider getting it ack in future ARC GNU tools as well as submitting it to upstream GCC.