Thanks for that patch.  After looking at it I added some more cleanup.

I saw one weird thing: we allow the --version option to be accepted from the environment:

$ MAKEFLAGS=--version make
GNU Make 4.3
  ...

and doesn't try to build any targets.  I don't think this is a good idea.  Anyone have a good reason to keep this behavior?

The reason GNU make behaves differently here is that for a normal program when you pipe its output the system automatically sets the stdout stream to block buffered mode (the default is line buffered mode).

This means that the entire version string is buffered in the stream, then it will be written as a single block when you flush (or exit, or the block fills up: but blocks are usually 1K or more so that won't happen for version info output).  Because it goes as a single block, the entire thing will be written to the pipe before the reader closes the pipe.

However, due to GNU make's output sync feature, make will force stdout to be in line buffered mode (where each line is flushed as its written) at all times.  This means that GNU make is writing its output in multiple separate system calls, which means it might get a write failure if the reader closes the pipe early.

Unfortunately I'm not sure there's a simple way to avoid this.  I'll have to think about it.

I'm not convinced that this is a bug.  First, it's highly timing-dependent: when I tried it it didn't fail:

$ make --version | head -n1
GNU Make 4.3

$ echo $?
0

Second, you can get similar behavior from other commands; you just have to be sure that the writer is still trying to write when the reader (head) has exited.  For example:

$ (/bin/echo one; sleep 1; /bin/echo hi) | head -n1
one
/bin/echo: write error: Broken pipe

$ echo $?
1

Here /bin/echo exits with 1 not 141 but it's the same thing with a different exit code.