Cleanup and improve Makefile

README.md

@@ -62,20 +62,13 @@ Schematic:
 
 ## How to build
 
-For GNU/Linux and Mac OS X:
+For GNU/Linux and macOS, you must have GCC or Clang installed. For Windows, w64-mingw32-gcc is required.
 
 ```
   cd inexact
   make
 ```
 
-For Microsoft Windows using cross compilation on GNU/Linux:
-
-```
-  cd inexact
-  make windows
-```
-
 ## Usage
 
 Asymmetric encryption:
@@ -139,4 +132,3 @@ Inexact is released under CC0 licence, except for this externals libraries:
 - https://nachtimwald.com/2017/09/24/hex-encode-and-decode-in-c/
 - https://github.com/argtable/argtable3
 - https://github.com/dsprenkels/randombytes
-