Update README.md to include setting up the build.sh environment

Author: tlundeen

README.md

@@ -5,9 +5,16 @@ Port of libiconv and libicu to Android
 
 You will need NDK r15, curl, autoconf, automake, libtool, and git installed.
 
-There are no sources and no patches - everything is done with magical build scripts,
-just run build.sh and enjoy.
-Don't forget to strip them, because they are huge with debug info included.
+There are no sources and no patches - everything is done with magical build scripts:
+
+(1) Make sure "which ndk-build" shows the correct version to build from
+
+(2) The scripts assume NDK/toolchain/... version 4.9. If otherwise, edit all the *.sh to
+    change GCCVER=4.9 as desired.
+
+(3) Run "./build.sh" and enjoy!
+
+(4) Don't forget to strip them, because they are huge with debug info included.
 
 There is no mips architecture, because there are very few devices using this architecture in the wild.