UI: fix desktop file for AppImage support

Author: chrisws

src/platform/fltk/Makefile.am

@@ -49,7 +49,7 @@ sbasici_DEPENDENCIES = $(top_srcdir)/src/common/libsb_common.a
 iconsdir = $(datadir)/icons/hicolor/128x128/apps
 icons_DATA = ../../../images/sb-desktop-128x128.png
 desktopdir = $(datadir)/applications
-desktop_DATA = ../sdl/smallbasic.desktop
+desktop_DATA = smallbasic.desktop
 
 if WITH_WIN32
 sbasici_LDADD += win.res

src/platform/fltk/smallbasic.desktop

@@ -0,0 +1,9 @@
+[Desktop Entry]
+Name=SmallBASIC
+Exec=sbasici
+Icon=sb-desktop-128x128
+Terminal=false
+Type=Application
+Categories=Development;
+MimeType=application/bas
+NoDisplay=false