"Trivial" changes like that contributes substantially to making projects hard to read and understand. When there are no better alternatives, that may be warranted, but in this case there is an obvious alternative: Fix the libc implementations that are incompatible with glibc, and at the same time gain the benefit of helping other applications.

I wish more projects would take this line.

Autoconf is the devil. It's a symptom of how broken Unix-y environments have been, and how people were willing to impart a massive maintenance cost of countless application code bases instead of either pushing their vendors to getting things right, or agreeing on common compatibility layers.