Make "unable to detect git commit" a debug message #1119

Job	Run time
Build melange and add to artifact cache	33s
Build packages (hello-wolfi)	1m 4s
Build packages (glibc)	1m 5s
Build packages (tini)	1m 2s
Build packages (lzo)	46s
Build packages (bubblewrap)	39s
Build packages (gdk-pixbuf)	46s
Build packages (gitsign)	2m 9s
Build packages (guac)	2m 54s
Build packages (mdbook)	3m 26s
Build packages (s3cmd)	52s
Build packages (perl-yaml-syck)	58s
Build packages (xmlto)	1m 1s
Build packages (ncurses)	1m 25s
	18m 40s

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