Fix FTBFS #962667
Import upstream commit : https://github.com/Ardour/ardour/commit/2a456c19214ce82c257a222e8de31af6113aa8d7 Also take that opportunity to implement get_cycles on ppc64.
Import upstream commit : https://github.com/Ardour/ardour/commit/2a456c19214ce82c257a222e8de31af6113aa8d7 Also take that opportunity to implement get_cycles on ppc64.