[clang] [RISCV] Merging RISCVToolChain and BareMetal toolchains (PR #118809)

[Garvit Gupta via cfe-commits]

quic-garvgupt wrote:

I have divided this PR into three separate PRs to streamline the review process and ensured that ARM and RISCV tests are not modified in the same PR. Please review them and provide any feedback or comments. Thanks!

[RISCV] Teach Barmetal toolchain about GCC installation(1/3) - https://github.com/llvm/llvm-project/pull/121831
[RISCV] Change linker job in Baremetal toolchain object accomodate GCCInstallation.(2/3) - https://github.com/llvm/llvm-project/pull/121830
[RISCV] Integrate RISCV target in baremetal toolchain object and deprecate RISCVToolchain object.(3/3) - https://github.com/llvm/llvm-project/pull/121829

https://github.com/llvm/llvm-project/pull/118809