tests/libfixmath: Add delay at start of test

The delay allows allows time for the `make term` to connect and start flushing the output buffer before the buffer overflows.

tests/libfixmath/Makefile

@@ -2,7 +2,8 @@ include ../Makefile.tests_common
 
 USEPKG += libfixmath
 USEMODULE += libfixmath
+USEMODULE += xtimer
 
-TEST_ON_CI_WHITELIST += native
+TEST_ON_CI_WHITELIST += all
 
 include $(RIOTBASE)/Makefile.include

tests/libfixmath/main.c

@@ -30,6 +30,7 @@
 
 #include <stdio.h>
 
+#include "xtimer.h"
 #include "fix16.h"
 
 #ifndef M_PI
@@ -184,6 +185,8 @@ static void unary_ops(void)
 
 int main(void)
 {
+    /* Delay output to prevent flooding of buffer */
+    xtimer_sleep(1);
     puts("Unary.");
     unary_ops();