lib: c: implement runtime initialisation

lib/libc/core/sys/x86_64/init.c

@@ -0,0 +1,18 @@
+#include <mango/log.h>
+#include <rosetta/bootstrap.h>
+#include <stdio.h>
+
+extern int main(int, const char **, const char **);
+
+void *__attribute__((weak)) pthread_self(void)
+{
+	/* Nothing */
+	return NULL;
+}
+
+int __libc_init(const struct rosetta_bootstrap *bsinfo)
+{
+	(volatile void)pthread_self();
+	kern_logf("bsinfo = %p", bsinfo);
+	return 0;
+}