android: util: Move xxd.py to util

android: util: Move xxd.py to util

Android porting of gen rules as per 22ffc05266c6 ("util: Move xxd.py to util")

Fixes the following building error:

ninja: error: 'external/mesa/src/compiler/glsl/xxd.py', needed by 'out/target/product/x86_64/gen/STATIC_LIBRARIES/libmesa_glsl_intermediates/glsl/float64_glsl.h', missing and no known rule to make it

Fixes: 22ffc05266c6 ("util: Move xxd.py to util")
Signed-off-by: Mauro Rossi <issor.oruam@gmail.com>
Reviewed-by: Jesse Natalie <jenatali@microsoft.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7087>