Building Firefox from pkgsrc-2015Q1 hangs

Hello,

I installed NetBSD 6.1_STABLE and try to compile firefox from pkgsrc-2015Q1.

The build hangs at:

----
checking how to hardcode library paths into programs... immediate
checking for exception model to use... call frame
checking for compiler with PCH support...
----

This "state" is displayed since yesterday evening.

"top" shows me that CPU1 is around 99% (system).

What to do?

btw: I tried out pkgsrc-2015Q2 but got an error with perl 5.22 (same as 
in VAX or MIPS (there was a post about it)).

Is there a repository with precompiled packages from which am I able to 
install this software?

Any ideas?

Greetings
Helge