What about this? Is this dead?

Was it ever alive? "This project has no files"

Not sure why you'd bother... GCC turns C (or C++, or Java, or ...) into assembler code. This is fed to a tool included in Binutils, known as "AS - the portable GNU assembler". Which -among many other architectures-, supports generating Z80 code (!). From that tools' man page:

Target Z80 options:
         [-z80] [-r800]
         [ -ignore-undocumented-instructions] [-Wnud]
         [ -ignore-unportable-instructions] [-Wnup]
         [ -warn-undocumented-instructions] [-Wud]
         [ -warn-unportable-instructions] [-Wup]
         [ -forbid-undocumented-instructions] [-Fud]
         [ -forbid-unportable-instructions] [-Fup]

So if you have a Linux or BSD based system, and installed packages include Binutils, good chance that does include a Z80 assembler.

Not to mention there exist several other C compilers that can produce Z80 code. For example sdcc (Small Device C Compiler).

SDCC is good enough.

I use it with Fuzix, and rlengine to make ROMS, and other people (like Konamiman) uses it to create MSXDOS software.

I recommend it. Have tried other options and I think is the best C cross-compiler that can be used with MSX at the moment.