libgflags-dev 2.2.2-1build1 (amd64 binary) in ubuntu focal

 gflags is a library that implements commandline flags processing. As
 such it's a replacement for getopt(). It has increased flexibility,
 including built-in support for C++ types like string, and the ability
 to define flags in the source file in which they're used.
 .
 This package contains development libraries and header files.