Have you tried running TIMEOUTFACTOR=16 make -k check 2>&1 | tee glibc-check-log
to eliminate test timeouts being exceeded as mentioned in chapter 6.9? Also check the created log files for time-outs (if they are time outs, then you are probably safe to ignore them).
Experience tells me that these 2 can probably be ignored:
make: *** [/sources/glibc-build/nptl/tst-cond20.out] Error 1
make: *** [/sources/glibc-build/nptl/tst-cond21.out] Error 1
This one I'm not sure about
make: *** [/sources/glibc-build/malloc/tst-trim1.out] Error 1
If you decide to ignore them, you will probably find out if all still works in the next chapter (6.10. Adjusting the Toolchain).