Applied theme and tested on several GTK applications as well as gtk3-demo samples
Also changed to meson build system, added builddep.
Setting DESTDIR should not be necessary if you're using the supported macros:
Yeah I tried using the macros but got errors hence using the base commands.
Seemed to work fine for @Gnat008 per R3334:bbf9ea2c4970492771abdd0ed08c96dbb5757188