LibC: Do not declare main as extern "C"

The linkage of `main` is implementation-defined in C++.

Author: implicitfield

Userland/Libraries/LibC/crt0.cpp

@@ -11,10 +11,10 @@
 #include <sys/internals.h>
 #include <unistd.h>
 
-extern "C" {
-
 int main(int, char**, char**);
 
+extern "C" {
+
 // Tell the compiler that this may be called from somewhere else.
 int _entry(int argc, char** argv) __attribute__((used));
 void _start(int, char**, char**) __attribute__((used));