Here is a full build log:

http://autobuild.buildroot.net/results/e4e/e4ee0ae40ac9d58b3182db52d5a39e6ac3692
f60/build-end.log

The relevant snippet is this one:

---------------------------------------
make[1]: Entering directory 
`/home/peko/autobuild/instance-1/output/build/tstools-1_11'
mkdir bin
mkdir lib
mkdir obj
/home/peko/autobuild/instance-1/output/host/usr/bin/mips64el-ctng_n32-linux-gnu-
gcc -c esfilter.c -o obj/esfilter.o -Wall -O2 -g -D_FILE_OFFSET_BITS=64 -I.  
-fPIC
/home/peko/autobuild/instance-1/output/host/usr/bin/mips64el-ctng_n32-linux-gnu-
gcc -c accessunit.c -o obj/accessunit.o -Wall -O2 -g -D_FILE_OFFSET_BITS=64 -I. 
 -fPIC
/home/peko/autobuild/instance-1/output/host/usr/bin/mips64el-ctng_n32-linux-gnu-
gcc -c avs.c -o obj/avs.o -Wall -O2 -g -D_FILE_OFFSET_BITS=64 -I.  -fPIC
Assembler messages:
Fatal error: can't create obj/esfilter.o: No such file or directory
---------------------------------------

I think this is a race condition problem due to the "obj" directory not being 
created in time.