> writing a shell script in C and calling GCC on every invocation. You can't expect good performance from that

Of course you can. Have you ever used the "-run" option of the TCC compiler? It's blazingly fast. With gcc it's a bit slower, but still orders of magnitude faster than julia. You can use pre-compiled libraries and the linking to your freshly compiled code is extremely fast. The fact is that compiling and linking C code is much faster that just launching the Julia environment with some packages. There's no fundamental reason for that enormous disparity in running time. I agree that it is a completely irrelevant nuisance for most people; but still, for some workflows not blessed by the Julia developers, it is the main point of friction.

EDIT: if you want to try it yourself, write the following text into a .c file, chmod +x it, and you can run it like a C script on most unix systems:

    //usr/bin/gcc -O0 "$0" -lpng && exec ./a.out "$@"
    #include <png.h>
    int main(int c, char *v[])
    {
            // do stuff with png images
            return 0;
    }