tools/intel_gpu_abrt: Fix bashism

intel-gpu-tools ships a #!/bin/sh script that has bash-specific syntax
(which breaks on distros such as Debian and Ubuntu where /bin/sh is a
symlink to something other than bash).

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=87888

tools/intel_gpu_abrt

@@ -1,6 +1,6 @@
 #!/bin/sh
 
-if [[ $UID -ne 0 ]]; then
+if [ $(id -ru) -ne 0 ]; then
     echo "$0 must be run as root"
     exit 1
 fi