Broken build with custom LDFLAGS

When building BIND I install with a per-build path in /opt so that I can roll forward / roll back easily. Instead of configuring the run-time linker, I use the linker -R flag to set the run path in the binary.

The essence is:

LDFLAGS="-Wl,-R$PREFIX/lib,-R$OpenSSL/lib" \
./configure 	--with-libfstrm=$PREFIX \
	--with-openssl=$OpenSSL \
	--prefix=$PREFIX

LD_RUN_PATH="$PREFIX/lib:$OpenSSL/lib" make all

LDFLAGS is a supported build environment variable (see BIND's README)

This configuration was broken by commit a0571d38, in particular the commit message says:

  - set LDFLAGS in the Makefile for dig so that, if specified, the requested libidn2 path is used when linking with libidn2,

This breaks my LDFLAGS setting so dig now fails to link.

The commands I used to blame this commit was

git bisect start master v9_13_0
git bisect run ../rebuild-bind.sh

rebuild-bind.sh