meson: fix installation with meson-python

The meson-python backend fails to map 'dtdiff' install into Python
wheels. Removing the prefix from the install_dir path allows
meson-python to map dtdiff. The install_data(install_dir) documentation
says "If this is a relative path, it is assumed to be relative to the
prefix"[1]. So removing the prefix does not change the installation
behaviour.

[1] https://mesonbuild.com/Reference-manual_functions.html#install_data

Signed-off-by: Brandon Maier <brandon.maier@collins.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

meson.build

@@ -122,7 +122,7 @@ if get_option('tools')
 
   install_data(
     'dtdiff',
-    install_dir: get_option('prefix') / get_option('bindir'),
+    install_dir: get_option('bindir'),
     install_mode: 'rwxr-xr-x',
   )
 endif