[PATCH 2/2] riscv: fix detection of toolchain Zihintpause support

[Heiko Stübner]

Am Donnerstag, 6. Oktober 2022, 19:35:21 CEST schrieb Conor Dooley:
> From: Conor Dooley <conor.dooley at microchip.com>
> 
> It is not sufficient to check if a toolchain supports a particular
> extension without checking if the linker supports that extension
> too. For example, Clang 15 supports Zihintpause but GNU bintutils
> 2.35.2 does not, leading build errors like so:
> 
> riscv64-linux-gnu-ld: -march=rv64i2p0_m2p0_a2p0_c2p0_zihintpause2p0: Invalid or unknown z ISA extension: 'zihintpause'
> 
> Add a TOOLCHAIN_HAS_ZIHINTPAUSE which checks if each of the compiler,
> assembler and linker support the extension. Replace the ifdef in the
> vdso with one depending on this new symbol.
> 
> Fixes: 8eb060e10185 ("arch/riscv: add Zihintpause support")
> Signed-off-by: Conor Dooley <conor.dooley at microchip.com>

Reviewed-by: Heiko Stuebner <heiko at sntech.de>