Does not build on riscv64

https://launchpad.net/ubuntu/+source/ltrace/0.7.3-6.1ubuntu2/+build/19524605

/usr/bin/make -C . 
make[1]: Entering directory '/<<PKGBUILDDIR>>'
/usr/bin/make  all-recursive
make[2]: Entering directory '/<<PKGBUILDDIR>>'
Making all in sysdeps
make[3]: Entering directory '/<<PKGBUILDDIR>>/sysdeps'
Making all in linux-gnu
make[4]: Entering directory '/<<PKGBUILDDIR>>/sysdeps/linux-gnu'
Making all in riscv64
/bin/bash: line 20: cd: riscv64: No such file or directory
make[4]: *** [Makefile:504: all-recursive] Error 1

It would be ni