I think I found the error. ./waf i18n_mo throws an error on gtk2_ardour/po/de.po and fails to compile the .mo file.
As a workaround you can open de.po in a text editor, locate line 2980 and you’ll see 2 times double backlashes. Remove one of them, so that the line reads
"Konnte Projekt in \"%1\" nicht erzeugen.\n"
This should fix .mo compilation and install.
Sorry for that, I have no idea how or when this crept in and why I (as german translator) didn’t realize earlier. I’ll care to get this fix upstream as soon as possible.
Hm I cannot reproduce this. But meanwhile the fix is on github, so just updating your sources to current and recompile without my modification should do it - I think I recompiled twice or three times from ground up yesterday for a different reason, and had no issues anymore.
Also may I ask why you run i18n_mo at all? As an end user you aren’t expected to do that, the translation files are generated automatically, during a normal ./waf build run.