Steps to reproduce the issue

$ spack install [email protected]
...
>> 29760    /apps/spack/var/spack/stage/gcc-7.2.0-bcsmtl56t3etoswkauritld6bzfnjfzx/gcc-7.2.0/libsanitizer/sanitizer_common/sanitizer_platform_limits_posix.cc:157:10: fatal error: sys/ustat.h: No such file or directory
     29761     #include <sys/ustat.h>
     29762              ^~~~~~~~~~~~~
     29763    compilation terminated.
...

Platform and user environment

Please report your OS here:

$ uname -a 
Linux glados 4.18.16-300.fc29.x86_64 #1 SMP Sat Oct 20 23:24:08 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux
$ lsb_release -d
Description:    Fedora release 29 (Twenty Nine)

Additional information

This issue is with the system glibc (2.28).
Broken versions are releases before 7.4.0 (Except 6.5.0 where I believe the fix was backported)

I have attached the patched used in the GCC 6.4.0 Arch Linux user repo package.

glibc2.28-ustat.patch.txt

I'm not sure if all the releases are broken, I think the required addition to the package.py is:

patch('glibc2.28-ustat.patch', when='@4:6.4,7:7.3')

I can submit a pull request if this looks correct