New stdin2out utility as replacement for tail -f

This little utility allows us to remove the noux instance for the log
view of Sculpt OS.

Issue #3696

repos/libports/recipes/src/stdin2out/content.mk

@@ -0,0 +1,10 @@
+MIRROR_FROM_REP_DIR := src/app/stdin2out
+
+content: $(MIRROR_FROM_REP_DIR) LICENSE
+
+$(MIRROR_FROM_REP_DIR):
+	$(mirror_from_rep_dir)
+
+LICENSE:
+	cp $(GENODE_DIR)/LICENSE $@
+

repos/libports/recipes/src/stdin2out/hash

@@ -0,0 +1 @@
+2020-03-25 35a1a6bf7235f21227af3c813c3527d26d06cffe

repos/libports/recipes/src/stdin2out/used_apis

@@ -0,0 +1,2 @@
+libc
+posix

repos/libports/src/app/stdin2out/main.cc

@@ -0,0 +1,31 @@
+/*
+ * \brief  Utility for forwarding data to stdout by polling stdin
+ * \author Norman Feske
+ * \date   2020-03-25
+ *
+ * This program fulfils the purpose of 'tail -f' for the log view of Sculpt OS.
+ */
+
+/*
+ * Copyright (C) 2020 Genode Labs GmbH
+ *
+ * This file is part of the Genode OS framework, which is distributed
+ * under the terms of the GNU Affero General Public License version 3.
+ */
+
+#include <unistd.h>
+
+extern "C" int main(int, char **)
+{
+	while (true) {
+
+		char buffer[4096] { };
+
+		size_t bytes = read(STDIN_FILENO, buffer, sizeof(buffer));
+
+		if (bytes == 0)
+			sleep(2);
+		else
+			write(STDOUT_FILENO, buffer, bytes);
+	}
+}

repos/libports/src/app/stdin2out/target.mk

@@ -0,0 +1,3 @@
+TARGET := stdin2out
+SRC_CC := main.cc
+LIBS   += posix