There are sample Makefile.gcc and Makefile.msc for pngcrush, which you can use
by typing, for example

    make -f Makefile.gcc

However, all you should need to do is enter the pngcrush-n.n.n
directory and type

    cc -O -o pngcrush *.c -lm
    cp pngcrush /usr/local/bin  # or wherever you want

You might want to create your own Makefile if you are planning to do
something more complicated, like loading with your system's shared
libraries for libpng and zlib.

Here's a command for compiling on SGI IRIX:

    cc -n32 -fullwarn -O2 -IPA:plimit=256 -OPT:Olimit=0 -o pngcrush *.c -lm
    cp pngcrush /usr/local/bin

On a PC with DJGCC, you can type

    gcc -O3 -Wall -funroll-loops -o pngcrush *.c
    copy /B pmodstub.exe + pngcrush pngcrush.exe

then put pngcrush.exe wherever you want.