Revert "Option --assume-execute-permission"

This reverts commit 4484acf9d6.

src/p_unix.cpp

@@ -68,10 +68,11 @@ bool PackUnix::canPack()
     if (exetype == 0)
         return false;
 
+#if defined(__unix__) && !defined(__MSYS2__)
     // must be executable by owner
-    if (!opt->o_unix.assume_execute_permission  // benefits __MSYS2__
-    &&  (fi->st.st_mode & S_IXUSR) == 0)
+    if ((fi->st.st_mode & S_IXUSR) == 0)
         throwCantPack("file not executable; try 'chmod +x'");
+#endif
     if (file_size < 4096)
         throwCantPack("file is too small");