test-lib: Work around incompatible sort and find on Windows

If the PATH lists the Windows system directories before the MSYS
directories, Windows's own incompatible sort and find commands would be
picked up. We implement these commands as functions and call the real
tools by absolute path.
Signed-off-by: NJohannes Sixt <j6t@kdbg.org>

t/test-lib.sh

@@ -635,3 +635,16 @@ do
 		test_done
 	esac
 done
+
+# Fix some commands on Windows
+case $(uname -s) in
+*MINGW*)
+	# Windows has its own (incompatible) sort and find
+	sort () {
+		/usr/bin/sort "$@"
+	}
+	find () {
+		/usr/bin/find "$@"
+	}
+	;;
+esac