Add option for standalone static binaries

[rcarmo]

I realize this might not be everyone's cup of tea, but I would like to see a configure option to build standalone static binaries (I'm currently trying to do this manually for shrpx, but it would be nice if it were possible to have for all binaries...)

[tatsuhiro-t]

Adding -all-static to LDFLAGS is the first step for statically linked binary, but I saw some problem with getaddrinfo and dlopen. The linker issues warning about them when linking, saying that same version of libc is required on runtime.

[rcarmo]

I see what you mean. Like you say, it's a first step, and might realistically be the simplest way to minimize runtime dependencies. I'm a bit spoiled by all the standalone Go binaries, and would like to use shrpx and the other binaries without worrying about dependencies.