fix(posix): include visibility.h for __EXPORT in common time.h

clang-tidy on Linux flagged \`unknown type name __EXPORT\` for
px4_clock_gettime / px4_clock_settime / px4_usleep / px4_sleep. The
declarations rely on the __EXPORT macro defined in visibility.h, which
the build system normally pulls in indirectly. Make the dependency
explicit so the header parses correctly when included standalone.

Signed-off-by: Nuno Marques <n.marques21@hotmail.com>

platforms/common/include/px4_platform_common/time.h

@@ -1,5 +1,7 @@
 #pragma once
 
+#include <visibility.h>
+
 #include <unistd.h>
 #include <sys/types.h>
 #include <time.h>