* tests/gzcompress_test.in: Skip if gzip is not installed (unlikely,

but for symmetry).
* tests/lzocompress_test.in: Skip if lzop is not installed.
* tests/xzcompress_test.in: Skip if xz is not installed.

tests/gzcompress_test.in

@@ -19,6 +19,11 @@ grubshell=@builddir@/grub-shell
 
 . "@builddir@/grub-core/modinfo.sh"
 
+if ! which gzip >/dev/null 2>&1; then
+   echo "gzip not installed; cannot test gzip compression."
+   exit 77
+fi
+
 if [ "$(echo hello | "${grubshell}" --mkrescue-arg=--compress=gz)" != "Hello World" ]; then
    exit 1
 fi