Fix problems with GCC optimization and cMake

[Xeratec]

Changelog

I noticed that GCCs tree-loop-distribute-patterns optimization can lead to infinite loops and stack overflows. This was tested with banshee simulations.

Further, the custom memcpy and memset implementation in software/runtime/string.c is sometimes swapped out with the GCC built-in function. However, this tends to lead to cause some bytes not to be copied if the number of bytes is at multiple of 4.

Finally, when using cMake with GCC, the configuration steps can fail because install/riscv-gcc/riscv32-unknown-elf/lib/riscv.ld is missing.

Fixed

• After building GCC, copy riscv.ld required for cMake to install folder
• Disable GCC tree-loop-distribute-patterns optimizations causing stack overflows
• Disable problematic GCC memset and memcpy built-in functions

Checklist

• Automated tests pass
• Changelog updated
• Code style guideline is observed

[SamuelRiedel]

LGTM. Thanks.