Fix Sim for newer distros

__builtin found fix for rbendian.h
tools/configure defines SIM_USE_BYTESWAP_H if byteswap.h is found in
/usr/include/ maybe there is a better mechanism for this

genshortcut.sh is a simple script to make .desktop shortcut files
several newer distros don't allow you to run the simulator from the
file manager, this or perhaps a different method can probably be
included while building a sim at a later date.

for now it can be run manually like so:
similar to ../tools/configure
run from your simulator folder
../tools/genshortcut.sh exepath shortname icon
ex. ../tools/genshortcut.sh ./rockboxui clip+sim music-app

Change-Id: Ia05d3a9349b27c5968a4a7a68b2eb480e60faec3

tools/configure

@@ -10,6 +10,9 @@
 # global CC options for all platforms
 CCOPTS="-W -Wall -Wundef -O -nostdlib -ffreestanding -Wstrict-prototypes -pipe -std=gnu99"
 
+#newer versions GLIBC use byteswap.h
+BYTESWP="/usr/include/byteswap.h"
+
 # LD options for the core
 LDOPTS=""
 # LD options for the core + plugins
@@ -4471,6 +4474,10 @@ fi
 if [ "yes" = "$simulator" ]; then
     echo Unsetting APPLICATION define for SIMULATOR build
     unset application
+    if test -f "$BYTESWP"; then
+        echo Using "$BYTESWP"
+        extradefines="$extradefines -DSIM_USE_BYTESWAP_H=$BYTESWP"
+    fi
 fi
 
 if [ "yes" = "$application" ]; then