Added jcpuid build instructions for linux/osx/freebsd/windows

core/c/README

@@ -1,3 +1,54 @@
+======
+JCPUID
+======
+
+Linux -> Windows cross-compilation
+----------------------------------
+Install ming-w64 (on debian or whichever package that provides i686-w64-mingw32 and x86_64_w64_mingw32).
+
+To build the 32-bit binaries run something like this:
+    CC=i686-w64-mingw32-gcc TARGET=windows BITS=32 ./build.sh
+
+To build the 64-bit binaries run something like this:
+    CC=x86_64-w64-mingw32-gcc TARGET=windows BITS=64 ./build.sh
+
+FreeBSD
+-------
+Compiled natively, x86 on a 32-bit install and x86_64 on a 64-bit install
+
+To build the 32-bit binaries run something like this:
+    BITS=32 ./build.sh
+
+To build the 64-bit binaries run something like this:
+    BITS=64 ./build.sh
+
+
+Linux
+-----
+Compiled natively x86 and x86_64 on a 64-bit install
+
+To build the 32-bit binaries run something like this:
+    BITS=32 ./build.sh
+
+To build the 64-bit binaries run something like this:
+    BITS=64 ./build.sh
+
+
+OSX
+---
+Compiled natively on OSX machine
+
+To build the 32-bit binaries run something like this:
+    BITS=32 ./build.sh
+
+To build the 64-bit binaries run something like this:
+    BITS=64 ./build.sh
+
+
+=====
+JBIGI
+=====
+
 
 Dynamic library build
 =====================