[arekm@carme-pld SPECS]$ strace -f -F -s 200 rpmbuild -bb alien.spec --target noarch 2>&1 | grep -E "rpm/.*/macros"
open("/usr/lib/rpm/noarch-/macros", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/etc/rpm/noarch-/macros", O_RDONLY) = -1 ENOENT (No such file or directory)

[arekm@carme-pld SPECS]$ strace -f -F -s 200 rpmbuild -bb alien.spec --target noarch-some-linux 2>&1 | grep -E "rpm/.*/macros"
open("/usr/lib/rpm/noarch-linux/macros", O_RDONLY) = 3
open("/etc/rpm/noarch-linux/macros", O_RDONLY) = -1 ENOENT (No such file or directory)