Compile fixes for old/unused targets.

These are some changes that I needed to compile
most of the unsupported targets.

After this all (make list_config_targets) compile
for me except: posix_eagle_muorb, posix_sdflight_default
and qurt_eagle_legacy_driver_default.

src/platforms/posix/tests/hrt_test/hrt_test.cpp

@@ -39,11 +39,13 @@
  * @author Mark Charlebois <charlebm@gmail.com>
  */
 
+#include "px4_log.h"
 #include <px4_time.h>
 #include <drivers/drv_hrt.h>
 #include "hrt_test.h"
 #include <unistd.h>
 #include <stdio.h>
+#include <cstring>
 
 px4::AppState HRTTest::appState;
 

src/platforms/qurt/tests/muorb/muorb_test_example.cpp

@@ -88,7 +88,7 @@ int MuorbTestExample::DefaultTest()
 
 	int i = 0;
 	pwm.error_count++;
-	sc.gyro_errcount[i]++;
+	/*sc.gyro_errcount[i]++;*/ // no member named 'gyro_errcount' in 'sensor_combined_s'
 
 	while (!appState.exitRequested() && i < 10) {
 
@@ -184,8 +184,8 @@ int MuorbTestExample::FileReadTest()
 	static const char TEST_FILE_PATH[] = "./test.txt";
 	FILE *fp;
 	char *line = NULL;
-	size_t len = 0;
-	ssize_t read;
+	/*size_t len = 0;
+	ssize_t read;*/
 
 	fp = fopen(TEST_FILE_PATH, "r");