Use getpagesize(3) under FreeBSD.

This avoids sysctl(2) syscall during binary startup, using the value
passed in the ELF aux vector instead.

Signed-off-by: Edward Tomasz Napierala <trasz@FreeBSD.org>

src/pages.c

@@ -357,6 +357,8 @@ os_page_detect(void) {
 	SYSTEM_INFO si;
 	GetSystemInfo(&si);
 	return si.dwPageSize;
+#elif defined(__FreeBSD__)
+	return getpagesize();
 #else
 	long result = sysconf(_SC_PAGESIZE);
 	if (result == -1) {