Enable readline and tcl in mxe builds

CodingReadme

@@ -411,6 +411,32 @@ Updating the website:
 	git commit -am update
 	make push
 
+
+
+Cross-Building for Windows with MXE
+===================================
+
+Check http://mxe.cc/#requirements and install all missing requirements.
+
+As root (or other user with write access to /usr/local/src):
+
+	cd /usr/local/src
+	git clone https://github.com/mxe/mxe.git
+	cd mxe
+
+	make -j$(nproc) MXE_PLUGIN_DIRS="plugins/tcl.tk" \
+			MXE_TARGETS="i686-w64-mingw32.static" \
+			gcc tcl readline
+
+Then as regular user in some directory where you build stuff:
+
+	git clone https://github.com/cliffordwolf/yosys.git yosys-win32
+	cd yosys-win32
+	make config-mxe
+	make -j$(nproc) mxebin
+
+
+
 How to add unit test
 ====================