This is z80asm, the Z80 Macro Assembler by Bas Wijnen.

How to install shevek's Z80 assembler

To install z80asm from the sources, you'll need the GNU autotools installed.

1. Preparation

Run autoreconf -fis to prepare the build

2. Configuration

Run ./configure for a standard installation to prefix /usr/local, with asembler header files installed into
/usr/local/share/z80asm. You can change the prefix by giving the --prefix=... parameter. For other options,
please see ./configure --help

3. Building the program

make all

builds the assembler and the documentation and runs tests.

4. Installation

sudo make install

installs everything to the configured prefix.