install.sh: check for rustc instead of rustup

[chapmanjacobd]

PR Info

Bug Fixes

I have rust installed via system package and no rustup. Seems like this check does more harm than good... unless this tool requires multiple rust toolchains for some reason

curl -s https://raw.githubusercontent.com/SeaQL/FireDBG.for.Rust/main/install.sh -sSf | sh
FireDBG: failed to find Rust installation, is rustup installed?

--- after this patch ---

bash t.sh
info: downloading FireDBG from `https://github.com/SeaQL/FireDBG.for.Rust/releases/download/1.81.0/x86_64-fedora39.tar.gz`
info: installing FireDBG binaries to `/home/xk/.cargo/bin`
info: performing FireDBG self tests
    Updating crates.io index
  Downloaded firedbg-lib v0.1.2
  Downloaded 1 crate (2.2 KB) in 0.96s
     Tracing `firedbg.toml` config file not found, default settings will be applied
     Tracing debugger_self_test = { trace = "full" }
      Parsed 2 source files; re-cached 2 source files
   Compiling firedbg-lib v0.1.2
   Compiling debugger_self_test v1.81.0 (/home/xk/.cargo/bin/firedbg-lib/debugger-self-test)
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.85s
     Running `LD_LIBRARY_PATH="/home/xk/.cargo/bin/firedbg-lib/lib" "/home/xk/.cargo/bin/firedbg-debugger" "run" "/home/xk/.cargo/bin/firedbg-lib/debugger-self-test/target/debug/debugger_self_test" "--workspace-root" "/home/xk/.cargo/bin/firedbg-lib/debugger-self-test" "--output" "/home/xk/.cargo/bin/firedbg-lib/debugger-self-test/output.firedbg.ss" "--package-name" "debugger_self_test" "--package" "./full"`
warning: (x86_64) /lib64/libgcc_s.so.1 No LZMA support found for reading .gnu_debugdata section
Testing call_chain
Testing for_range
Testing hash_map
Testing return_char
Testing return_enum
Testing return_value
Testing return_object
Testing return_option
Testing return_result
Testing return_struct
Testing return_pointer
Testing return_ref_mut
Testing fn_return
info: completed FireDBG self tests