Makefile for Google brotli and zopfli

I would like to include Google brotli and zopfli (incl. libzopfli and zopflipng) into my custom OpenWRT build. Has anybody already done this and can share the Makefile? I could not find anything on github.

Here is the source for both programs:

Build instructions for brotli and zopfli are:
The basic commands to build and install brotli are:

$ mkdir out && cd out
$ cmake -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=./installed ..
$ cmake --build . --config Release --target install

The source code of Zopfli is under src/zopfli. Build instructions:
To build zopfli, compile all .c source files under src/zopfli to a single binary
with C, and link to the standard C math library, e.g.:
gcc src/zopfli/*.c -O2 -W -Wall -Wextra -Wno-unused-function -ansi -pedantic -lm -o zopfli

I am completely new to writing Makefiles (have so far only done minor modifications to an existing Makefile) and need some help in creating them.

Many thanks!

Thank you, but unfortunately that does not solve my problem with brotli and zopfli. There are more complex than "hello world!". As I have written, my question was specifically about these two.