Cannot compile 8.10.5 on FreeBSD: "undefined reference to libiconv"

Happens with gmake and hadrian. As a side note: hadrian/ subdir doesn't exist in the generated source tarball, so I had to git clone, which took probably half an hour.

Configure line (as per GHC CI):

./configure --with-gmp-includes=/usr/local/include --with-gmp-libraries=/usr/local/lib --with-iconv-includes=/usr/local/include --with-iconv-libraries=/usr/local/lib

Error:

| Run Ghc CompileHs Stage1: libraries/text/src/Data/Text/Internal/Encoding/Utf32.hs => _build/stage1/libraries/text/build/Data/Text/Internal/Encoding/Utf32.o
ld.lld: error: _build/stage1/lib/../lib/x86_64-freebsd-ghc-8.10.5/libHSbase-4.14.2.0-ghc8.10.5.so: undefined reference to libiconv
ld.lld: error: _build/stage1/lib/../lib/x86_64-freebsd-ghc-8.10.5/libHSbase-4.14.2.0-ghc8.10.5.so: undefined reference to libiconv_close
ld.lld: error: _build/stage1/lib/../lib/x86_64-freebsd-ghc-8.10.5/libHSbase-4.14.2.0-ghc8.10.5.so: undefined reference to libiconv_open
cc: error: linker command failed with exit code 1 (use -v to see invocation)
`cc' failed in phase `Linker'. (Exit code: 1)
| Run Ghc CompileHs Stage1: libraries/ghc-boot/GHC/Settings.hs => _build/stage1/libraries/ghc-boot/build/GHC/Settings.p_o
ghc: interrupted
Error when running Shake build system:
  at action, called at src/Rules.hs:71:19 in main:Rules
  at need, called at src/Rules.hs:93:5 in main:Rules
* Depends on: _build/stage1/bin/runghc
* Raised the exception:
user error (Development.Shake.cmd, system command failed
Command line: _build/stage0/bin/ghc -Wall -hisuf dyn_hi -osuf dyn_o -hcsuf dyn_hc -fPIC -dynamic -hide-all-packages -no-user-package-db '-package-db _build/stage1/lib/package.conf.d' '-package-id base-4.14.2.0' '-package-id directory-1.3.6.0' '-package-id filepath-1.4.2.1' '-package-id process-1.6.9.0' '-package-id unix-2.7.2.2' -i -i_build/stage1/utils/runghc/build -i_build/stage1/utils/runghc/build/runghc/autogen -iutils/runghc/. -Iincludes -I_build/stage1/lib -I_build/stage1/utils/runghc/build -I/usr/local/include -I/usr/local/include -I/home/hasufell/ghc/_build/stage1/lib/x86_64-freebsd-ghc-8.10.5/process-1.6.9.0/include -I/home/hasufell/ghc/_build/stage1/lib/x86_64-freebsd-ghc-8.10.5/unix-2.7.2.2/include -I/home/hasufell/ghc/_build/stage1/lib/x86_64-freebsd-ghc-8.10.5/time-1.9.3/include -I/home/hasufell/ghc/_build/stage1/lib/x86_64-freebsd-ghc-8.10.5/bytestring-0.10.12.0/include -I/usr/local/include -I/home/hasufell/ghc/_build/stage1/lib/x86_64-freebsd-ghc-8.10.5/base-4.14.2.0/include -I/usr/local/include -I/home/hasufell/ghc/_build/stage1/lib/x86_64-freebsd-ghc-8.10.5/integer-gmp-1.0.3.0/include -I/home/hasufell/ghc/_build/stage1/lib/x86_64-freebsd-ghc-8.10.5/rts-1.0.1/include -I_build/stage1/lib -optc-I_build/stage1/lib -optP-include -optP_build/stage1/utils/runghc/build/runghc/autogen/cabal_macros.h -outputdir _build/stage1/utils/runghc/build -dynamic -optl-Wl,-rpath,$ORIGIN/../lib/x86_64-freebsd-ghc-8.10.5 -optl-Wl,-rpath,$ORIGIN/../../../lib/x86_64-freebsd-ghc-8.10.5 -optl-Wl,-zorigin -no-auto-link-packages -rtsopts -Wnoncanonical-monad-instances -optc-Wno-unknown-pragmas _build/stage1/utils/runghc/build/Main.dyn_o -o _build/stage1/bin/runghc -O2 -H32m -XHaskell2010 -ghcversion-file=/home/hasufell/ghc/_build/stage1/lib/ghcversion.h
Exit code: 1
Stderr:
ld.lld: error: _build/stage1/lib/../lib/x86_64-freebsd-ghc-8.10.5/libHSbase-4.14.2.0-ghc8.10.5.so: undefined reference to libiconv
ld.lld: error: _build/stage1/lib/../lib/x86_64-freebsd-ghc-8.10.5/libHSbase-4.14.2.0-ghc8.10.5.so: undefined reference to libiconv_close
ld.lld: error: _build/stage1/lib/../lib/x86_64-freebsd-ghc-8.10.5/libHSbase-4.14.2.0-ghc8.10.5.so: undefined reference to libiconv_open
cc: error: linker command failed with exit code 1 (use -v to see invocation)
`cc' failed in phase `Linker'. (Exit code: 1)
)

This was confirmed by other FreeBSD users on IRC. However, it seemed that @trac-vdukhovni had a script that allowed him to build, but he got cut off of IRC before he could share more.