Checking for if.h during configure produces a warning
checking net/if.h presence... yes
configure: WARNING: net/if.h: present but cannot be compiled
configure: WARNING: net/if.h: check for missing prerequisite headers?
configure: WARNING: net/if.h: see the Autoconf documentation
configure: WARNING: net/if.h: section "Present But Cannot Be Compiled"
configure: WARNING: net/if.h: proceeding with the compiler's result
checking for net/if.h... no
Looks like that got introduced in 9f06ec0c13f0b25ce3bb2c0c352edb04083dbe2c