Update custom rustc instructions

Author: antoyo

.github/workflows/main.yml

@@ -66,6 +66,7 @@ jobs:
       run: |
         ./prepare_build.sh
         ./build.sh
+        cargo test
         ./clean_all.sh
 
     - name: Prepare dependencies

.gitignore

@@ -15,3 +15,4 @@ gimple*
 *asm
 res
 test-backend
+gcc_path

Readme.md

@@ -113,6 +113,5 @@ p loc->m_line
 
 ### How to use a custom-build rustc
 
- * Build the stage1 compiler (`rustup toolchain link debug-current stage2 build/x86_64-unknown-linux-gnu/stage1`).
+ * Build the stage2 compiler (`rustup toolchain link debug-current build/x86_64-unknown-linux-gnu/stage2`).
  * Clean and rebuild the codegen with `debug-current` in the file `rust-toolchain`.
- * Add `~/.rustup/toolchains/debug-current/lib/rustlib/x86_64-unknown-linux-gnu/lib` to `LD_LIBRARY_PATH`.