Use of # character in nim version path makes CMake compilation fail
Building `drnim` tool in current `nim-#devel` compiles the Z3 library from sources using cmake. But the presence of a `#` character in choosenim toolchains path makes the compilation fail.
```
$ pwd
/home/pmetras/.choosenim/toolchains/nim-#devel

$ ./koch temp
bin/nim c -d:debug --debugger:native -d:nimBetterRun  -d:leanCompiler /home/pmetras/.choosenim/toolchains/nim-#devel/compiler/nim
Hint: used config file '/home/pmetras/.choosenim/toolchains/nim-#devel/config/nim.cfg' [Conf]

...

-- Z3_DEPENDENT_EXTRA_CXX_LINK_FLAGS: 
-- CMAKE_INSTALL_LIBDIR: "lib"
-- CMAKE_INSTALL_BINDIR: "bin"
-- CMAKE_INSTALL_INCLUDEDIR: "include"
-- CMAKE_INSTALL_PKGCONFIGDIR: "lib/pkgconfig"
-- CMAKE_INSTALL_Z3_CMAKE_PACKAGE_DIR: "lib/cmake/z3"
-- Adding component util
-- Adding component polynomial
-- Adding rule to generate "algebraic_params.hpp"
CMake Error at cmake/z3_add_component.cmake:118 (add_custom_command):
  add_custom_command called with OUTPUT containing a "#".  This character is
  not allowed.
Call Stack (most recent call first):
  src/math/polynomial/CMakeLists.txt:1 (z3_add_component)

...
```

I would say that is more a [cmake bug](https://gitlab.kitware.com/cmake/cmake/-/issues/12877) than a choosenim one, but the easiest workaround at the present time would be for choosenim to use a different path name.