Tweak the curl-impersonate build system to make it work on Red Hat
based systems such as CentOS, Fedora and Amazon Linux.
* Change the Makefile to be more portable with different bash versions.
* Detect whether cmake is 'cmake' or 'cmake3', and whether ninja is
'ninja' or 'ninja-build'.
* Explicitly tell brotli to put its libraries in 'lib' dir, otherwise it
might put them in 'lib64' where curl doesn't find them.
* Add instructions for building curl-impersonate from source on Red Hat
based systems.
Use a 'configure' script generated by autoconf to configure whether a
static build is desired, and where to install the final curl-impersonate
binaries. Add installation targets to the Makefile.
