[Bug libstdc++/124268] `import std` initializer symbol is not shipped in `libstdc++`

[bugzilla.gcc at me dot benboeckel.net via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=124268

--- Comment #2 from Ben Boeckel <bugzilla.gcc at me dot benboeckel.net> ---
Yes.

```
#!/bin/sh

cat >main.cpp <<EOF
import std;

int main(int argc, char* argv[])
{
  if (argc > 0 && argv[0]) {
    std::string argv0 = argv[0];
    std::print("program: {}/n", argv0);
  }
  return 0;
}
EOF

cat >modmap <<EOF
\$root .
std std.bmi
EOF

set -x
homebrew_prefix="/opt/homebrew/Cellar/gcc/15.2.0_1"

"$homebrew_prefix/bin/g++-15" -Drsize_t=ssize_t -std=gnu++26 -fmodule-only
-fmodules-ts -x c++ -o std.bmi -c "$homebrew_prefix/include/c++/15/bits/std.cc"
"$homebrew_prefix/bin/g++-15" -Drsize_t=ssize_t -std=gnu++26 -fmodules-ts
-fmodule-mapper=modmap -x c++ -o main.o -c main.cpp
"$homebrew_prefix/bin/g++-15" -std=gnu++26 -o main main.o
```