gcc-sanitizers: Add riscv64 as compatible host

gcc-sanitizers: Add riscv64 as compatible host

RISC-V offers several virtual memory address schemes (Sv39, Sv48, and Sv57),
but ASan currently supports only Sv39 on RISC-V64.
For RISC-V64 Sv39, ASan uses custom allocator configurations
tuned to manage large allocations efficiently.
These tunings are incompatible with larger address spaces like
Sv48/Sv57 due to differences in region sizes and alignment.

For riscv64, Asan's tuning for Sv39 can be enabled in qemu
by using the appropriate flag in the command line as shown below:
runqemu nographic qemuparams="-cpu rv64,sv39=true"

Additionally, the COMPATIBLE_HOST list in gcc-sanitizers has been
updated to include riscv64. All necessary tests were successfully
conducted on both hardware(Microchip PolarFire SoC)
and the qemurisv64 environment, with ASan effectively
detecting memory errors in both scenarios.

Signed-off-by: Deepthi Hemraj <Deepthi.Hemraj@windriver.com>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>