Only run mandoc test if mandoc is available

Makefile

@@ -4,7 +4,6 @@ all:
 	@${MAKE} -C src
 
 test: all
-	@mandoc -Tlint man/*
 	@PACKAGE=${PACKAGE} VERSION=${VERSION} prove test
 
 install: install-man install-doc install-bin install-font install-img

test/mandoc.t

+#!/usr/bin/env perl
+use strict;
+use warnings;
+use 5.010;
+
+use Test::More tests => 3;
+
+SKIP: {
+	qx{mandoc -V};
+
+	if ($? != 0) {
+		skip('mandoc not installed', 3);
+	}
+
+	for my $file ('feh', 'feh-cam', 'gen-cam-menu') {
+		qx{mandoc -Tlint man/${file}.1};
+		is($?, 0, "${file}.1: Valid mdoc syntax");
+	}
+}