Avoid racy depmodes with universal builds. * m4/depend.m4 (_AM_DEPENDENCIES): If universal builds are used, avoid racy depmodes. * lib/depcomp: Ignore `-arch' argument for makedepend depmode. Report by Bruno Haible, analysis by Bruno Haible, Peter O'Gorman, and Eric Blake. Signed-off-by: Ralf Wildenhues <Ralf.Wildenhues@gmx.de>