update readme to add better build instructions

README.org

@@ -31,12 +31,14 @@ Undâr is intended to run on anything with a C compiler. From constrained system
 ** Requirements
 *** Main
 - Git
-- C compiler
+- POSIX compliant shell (sh)
+- C compiler that supports C89
 *** Optional
+- C compiler that supports ANSI C or later
 - SDL2
   - For GUI linux and web versions
 - Emscripten
-  - For web version
+  - For building the web version
 
 ** Build
 
@@ -47,6 +49,22 @@ git clone https://git.alfrescocavern.com/zongor/undar-lang.git
 cd undar-lang && ./build
 #+END_SRC
 
+*** Build commands
+- clean
+  deletes the build files for that arch
+- run
+  runs that arch
+*** Build settings
+**** ARCH
+- linux
+- web
+**** MODE
+- debug
+- release
+**** UI
+- tui
+- gui
+
 * Roadmap
 
 [[./ROADMAP.org][Compiler, Plex, Immidate mode GUI, Constructive solid geometry, Tunnels, Actor model]]