Select compiler to use. Update README

Author: mcarans

README.md

@@ -1,14 +1,14 @@
 # Oolite MSYS2 MinGW64 Environment
 
-Creates MSYS2 MinGW64 packages of dependencies that Oolite needs
+Creates MSYS2 MinGW64 packages of dependencies that Oolite needs including both clang and gcc versions for the GNUStep libraries.
 
-You can also create an environment locally, building all dependencies, as follows:
+You can also create an environment locally, building all dependencies from source, as follows:
 
-Double click Run Me. You will be prompted for an install location. If you type c:, MSYS2 will be installed in c:\msys64. Then Oolite's dependencies will be installed followed by Oolite itself. A gcc build is created by default. 
+Double click Run Me. You will be prompted for an install location. If you type c:, MSYS2 will be installed in c:\msys64. You will then be prompted for the compiler to use. Type gcc or clang as desired. Then Oolite's dependencies will be built from source followed by Oolite itself.
 
 Once completed, you can type the following in the shell: 
 
     cd oolite/oolite.app
 	./oolite.exe
-	
-By default, install.sh is run with parameter gcc by setup.cmd (which is started by Run Me). install.sh can be run with parameter clang for a clang build. The GitHub Action passes no parameters which creates a clang build followed by a gcc build.
+
+Run Me is a shortcut which runs setup.cmd. setup.cmd installs MSYS2. It passes parameter gcc or clang to install.sh. install.sh builds Oolite's dependencies from source and then Oolite. The GitHub Action passes no parameters which creates a clang build followed by a gcc build of Oolite.

setup.cmd

@@ -8,6 +8,9 @@ echo Running in: %CD%
 :: Prompt the user for a path
 set /p INSTALL_PATH=Enter the installation path: 
 
+:: Prompt the user for whether to install gcc or clang
+set /p GCC_OR_CLANG=Enter compiler to use - gcc or clang: 
+
 :: Where to download installer
 set MSYS2_URL=https://github.com/msys2/msys2-installer/releases/latest/download/msys2-base-x86_64-latest.sfx.exe
 set INSTALLER=%TEMP%\msys2-base.sfx.exe
@@ -30,6 +33,6 @@ set MSYS2_ROOT=%INSTALL_PATH%\msys64
 %MSYS2_ROOT%\usr\bin\bash -lc "pacman -Syu --noconfirm"
 
 echo === Launch MinGW64 shell, build Oolite dependencies install Oolite  ===
-%MSYS2_ROOT%\msys2_shell.cmd -mingw64 -defterm -here -no-start -c "./install.sh gcc; exec bash"
+%MSYS2_ROOT%\msys2_shell.cmd -mingw64 -defterm -here -no-start -c "./install.sh %GCC_OR_CLANG%; exec bash"
 
 endlocal