perf.SlackBuild: fatal: Can't find kernel source in "/usr/src/linux-4.4.276"

Please make sure the correct version of the kernel source is
installed, and/or set the KERNEL environment variable to one of:

- The full path to the kernel source, e.g. KERNEL="/usr/src/linux-4.4.227"
- Or, the kernel version e.g. KERNEL="4.4.227"
100%100%Done
fakeroot -- sh perf.SlackBuild Failed