@Kha I had to comment the following lines. It is unclear what is going
on. All stages were building on my machine until I tried to build
using a fresh `build/release` directory. Then, I managed to reproduce
the error in the CI earlier today.
So, I destructively removed the `update-stage0`, and tried to build
using a fresh `build/release`. Then, I get the following error at
stage 1.
```
error: no such file or directory (error code: 2)
file: /Users/leonardodemoura/projects/lean4/build/release/stage1/bin/../lib/lean/Std
```
The error seems to be produced by the line I have commented. It is
a weird bug since I do have the directory
```
/Users/leonardodemoura/projects/lean4/build/release/stage1/lib/lean/Std
```
Note that it works for
```
/Users/leonardodemoura/projects/lean4/build/release/stage1/bin/../lib/lean/Init`
```
No idea why it doesn't work for `Std`.
Anyway, by commenting the lines in this commit I can build all stages
locally. The test `binomial.lean` doesn't work since `Std` is not in
the builtin path.
@Kha
I was having several errors of the form
```
224: /Users/leonardodemoura/projects/lean4/build/release/stage0.5/bin/../include/lean/runtime/exception.h:23:13: error: exception specification of overriding function is more lax than base version
224: virtual ~throwable() noexcept;
224: ^
224: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/exception:102:13: note: overridden virtual function is here
224: virtual ~exception() _NOEXCEPT;
224: ^
224: In file included from myfuns.cpp:1:
```
As far as I can tell, the error ocurrs because my compiler uses an old
C++ standard if the option `-std` is not used.
I guess `-std=c++11` would also works, but I decided to use the same
standard we used to compile Lean.
