Implement the way to run posix simulator directly from IDE without the need to reconfigure command lines, but use runner created via CMake

Steps to debug:
 * Run gazebo (or any other sim) server and client viewers via the terminal: `make posix_sitl_default gazebo_none_ide`
 * In your IDE select `px4_<mode>` target you want to debug (e.g. `px4_iris`)
 * Start debug session directly from IDE

This approach significantly reduces the debug cycle time because simulator (e.g. gazebo) is always running in background and you only re-run px4 process which is very light.

src/platforms/posix/main.cpp

@@ -286,7 +286,13 @@ static void set_cpu_scaling()
 #endif
 }
 
+#ifdef __PX4_SITL_MAIN_OVERRIDE
+int SITL_MAIN(int argc, char **argv);
+
+int SITL_MAIN(int argc, char **argv)
+#else
 int main(int argc, char **argv)
+#endif
 {
 	bool daemon_mode = false;
 	bool chroot_on = false;

src/platforms/posix/sitl_runner_main.cpp.in

@@ -0,0 +1,53 @@
+/****************************************************************************
+ *
+ *   Copyright (C) 2015 Anton Matosov. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name PX4 nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+/**
+ * @file sitl_runner_main.cpp
+ * Basic shell to execute px4 with specific model
+ *
+ * @author Anton Matosov <anton.matosov@gmail.com>
+ */
+
+#include <unistd.h>
+
+#define __PX4_SITL_MAIN_OVERRIDE
+#include "@SITL_RUNNER_MAIN_CPP@"
+
+int main(int argc, const char **argv)
+{
+    if (chdir("@SITL_RUNNER_WORKING_DIRECTORY@") != 0) {
+        PX4_ERR("Failed to change current directory to @SITL_RUNNER_WORKING_DIRECTORY@. error %i", errno);
+        return errno;
+    }
+    const char *argsOverride[] = {argv[0], "@SITL_RUNNER_SOURCE_DIR@", "@SITL_RUNNER_MODEL_FILE@"};
+    return SITL_MAIN(sizeof(argsOverride) / sizeof(argsOverride[0]), (char**)argsOverride);
+}