ZTS: Specify sysconfdir

On Linux distros like Arch Linux, files that should be in /etc/zfs end
up being installed in /usr/etc/zfs. Specifying sysconfdir path fixes it.

Signed-off-by: Kazuki Hashimoto <[email protected]>

Author: Kaz205

.github/workflows/scripts/qemu-4-build.sh

@@ -56,7 +56,8 @@ function linux() {
     --prefix=/usr \
     --enable-pyzfs \
     --enable-debug \
-    --enable-debuginfo
+    --enable-debuginfo \
+    --sysconfdir=/etc
   echo "##[endgroup]"
 
   echo "##[group]Build"