user: implement mlibc as the libc, finally.

It's finally done..

Signed-off-by: kaguya <vpshinomiya@protonmail.com>

user/include/mlibc/tests/rtld/ifunc-dlopen/test.c

@@ -0,0 +1,23 @@
+#include <assert.h>
+#include <dlfcn.h>
+
+int foo(void);
+
+#ifdef USE_HOST_LIBC
+#define LIB "libnative-ifunc-test-dlopen.so"
+#else
+#define LIB "libifunc-test-dlopen.so"
+#endif
+
+int main(void) {
+	void *handle = dlopen(LIB, RTLD_NOW | RTLD_LOCAL);
+	assert(handle);
+
+	int (*func)() = (int (*)()) dlsym(handle, "foo");
+	assert(func);
+
+	int ret = func();
+	assert(ret == 69);
+
+	return 0;
+}