libc: silence noncritical dummy implementations

* isatty

  For the moment it is not possible to determine if the fd belongs to a
  tty. For whatever reasons, the check is done multiple times, e.g.
  'tclsh', which will spam the LOG.

* sysctl(HW_FLOATINGPT)

  FPU is enabled on all our platforms, so return true.

Fixes #3389.

repos/libports/src/lib/libc/dummies.cc

@@ -100,7 +100,7 @@ DUMMY(pid_t , -1, getpgrp, (void))
 DUMMY(int   , -1, getpriority, (int, int))
 DUMMY(int   , -1, getrusage, (int, rusage *))
 DUMMY(uid_t ,  0, getuid, (void))
-DUMMY(int   ,  1, isatty, (int))
+DUMMY_SILENT(int   ,  1, isatty, (int))
 DUMMY(int   , -1, kill, (pid_t, int))
 DUMMY(int   , -1, link, (const char *, const char *))
 DUMMY(int   ,  0, minherit, (void *, size_t, int))

repos/libports/src/lib/libc/sysctl.cc

@@ -100,6 +100,14 @@ extern "C" int __sysctl(const int *name, u_int namelen,
 				*(int*)oldp = (int)PAGESIZE;
 				*oldlenp = sizeof(int);
 				return 0;
+			/*
+			 * Used on ARM platforms to check HW fp support. Since the
+			 * FP is enabled on all our ARM platforms we return true.
+			 */
+			case HW_FLOATINGPT:
+				*(int*)oldp = 1;
+				*oldlenp = sizeof(int);
+				return 0;
 
 			} break;