Regression in libnl3 detection (no longer uses pkg-config)

[thesamesam]

Hi!

We had a report in Gentoo of htop-3.4.0 failing to build on Gentoo Prefix (https://bugs.gentoo.org/951290), which is like a Homebrew/nix/whatever setup where Gentoo resides in /home/sam/prefix as an unprivileged prefix.

Since 24b1513, configure fails with:

[...]
checking for netlink/attr.h... no
configure: error: can not find required header files netlink/attr.h, netlink/handlers.h, netlink/msg.h

... because it now hardcodes CFLAGS="$CFLAGS -I/usr/include/libnl3" rather than using pkg-config via PKG_CHECK_MODULES.

[thesamesam]

cc @cgzones

[thesamesam]

Ah, I see #1637 already.