ltrace: bump to version 0.7.2

Bump ltrace to version 0.7.2 which includes my ppc fixup patch.
Also exclude aarch64 since it's not supported, fixes
http://autobuild.buildroot.net/results/8fc3a3720d9be2525784b0488653b4fdbb29e676/



Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>