Add sys_exec () and libprocess wrapper, fix ramdisk tar parsing

kernel/libk/string.h

@@ -8,6 +8,7 @@ size_t memcpy (void* dst, const void* src, size_t n);
 void strncpy (char* dst, const char* src, size_t n);
 size_t strlen (const char* str);
 int memcmp (const void* s1, const void* s2, size_t n);
+int strncmp (const char* s1, const char* s2, size_t n);
 
 #define strlen_null(x) (strlen ((x)) + 1)