right, this was simple, I created a mkdir befor the 'cd' in the spec to 'locale'.
It's a suse RPM.

Now I got another error:

+ mkdir -p /usr/src/packages/BUILDROOT/ardour-2.8.11-3.6.x86_64/usr/share/locale                                                              
+ cd /usr/src/packages/BUILDROOT/ardour-2.8.11-3.6.x86_64/usr/share/locale                                                                    
+ for i in de_DE el_GR es_ES fr_FR it_IT pl_PL pt_PT ru_RU sv_SE                                                                              
+ test -d de_DE                                                                                                                               
+ continue
+ for i in de_DE el_GR es_ES fr_FR it_IT pl_PL pt_PT ru_RU sv_SE
+ test -d el_GR
+ continue
+ for i in de_DE el_GR es_ES fr_FR it_IT pl_PL pt_PT ru_RU sv_SE
+ test -d es_ES
+ continue
+ for i in de_DE el_GR es_ES fr_FR it_IT pl_PL pt_PT ru_RU sv_SE
+ test -d fr_FR
+ continue
+ for i in de_DE el_GR es_ES fr_FR it_IT pl_PL pt_PT ru_RU sv_SE
+ test -d it_IT
+ continue
+ for i in de_DE el_GR es_ES fr_FR it_IT pl_PL pt_PT ru_RU sv_SE
+ test -d pl_PL
+ continue
+ for i in de_DE el_GR es_ES fr_FR it_IT pl_PL pt_PT ru_RU sv_SE
+ test -d pt_PT
+ continue
+ for i in de_DE el_GR es_ES fr_FR it_IT pl_PL pt_PT ru_RU sv_SE
+ test -d ru_RU
+ continue
+ for i in de_DE el_GR es_ES fr_FR it_IT pl_PL pt_PT ru_RU sv_SE
+ test -d sv_SE
+ continue
+ cp -v /usr/src/packages/SOURCES/ChangeLog ./
`/usr/src/packages/SOURCES/ChangeLog' -> `./ChangeLog'
+ /usr/lib/rpm/find-lang.sh /usr/src/packages/BUILDROOT/ardour-2.8.11-3.6.x86_64 libardour2 ardour.lang
No translations found for libardour2 in /usr/src/packages/BUILDROOT/ardour-2.8.11-3.6.x86_64

I'm using US-language and don't need lang-support.

Thanks for your help!

Yosef