Moved stdlib to a seperate folder and added some more headers that are required for compiling libgcc (no implementation yet).

targets/_any/stdlib/include/unistd.h

@@ -0,0 +1,22 @@
+
+#pragma once
+
+#if !defined(BAD_APPLE_OS_UNISTD_H_INCLUDED)
+#define BAD_APPLE_OS_UNISTD_H_INCLUDED
+
+#include <stdint.h>
+#include <sys/types.h>
+
+#include "./detail/common.h"
+
+BA_EXTERN_C_BEGIN
+
+pid_t fork() BA_CXX_NOEXCEPT;
+int execv(const char* pathname, char* const argv[]) BA_CXX_NOEXCEPT;
+int execve(const char* pathname, char* const argv[], char* const envp[]) BA_CXX_NOEXCEPT;
+int execvp(const char* file, char* const argv[]) BA_CXX_NOEXCEPT;
+pid_t getpid() BA_CXX_NOEXCEPT;
+
+BA_EXTERN_C_END
+
+#endif // !defined(BAD_APPLE_OS_UNISTD_H_INCLUDED)