Update README.md build instructions

README.md

@@ -1,5 +1,6 @@
+# Tricore GCC 11.3
 
-# Build instructions (Ubuntu)
+## Build native linux toolchain (Ubuntu)
 
 Clone the repository:
 
@@ -19,7 +20,20 @@ It is also possible to compile single components of the toolchain. For further i
 ./build-toolchain --help
 ```
 
-# Build instructions (Windows 10/11)
+## Cross-compile Windows toolchain from Linux (Ubuntu)
+
+It is possible to build the windows version of tricore-elf-gcc directly from
+a linux system using the MinGW cross-compiler available from ubuntu/debian
+repositories.
+
+For a list of software dependencies, refer to the
+[GitHub Action pipeline script](./.github/workflows/build.yml).
+
+To cross-compile the toolchain run the `build-toolchain-mingw` script. Please
+note that the script is meant to work from a Ubuntu/Debian distribution. For
+any other linux distribution, manual setup may be required.
+
+## Build instructions (Windows 10/11)
 
 Install the MSYS2 environment following the instructions available in the official website: https://www.msys2.org/