Error installing nq, anupq because GMP can't be found

[fingolfin]

julia> GAP.Packages.install("nq"; debug=true)
#I  Getting PackageInfo URLs...
#I  Retrieving PackageInfo.g from https://gap-packages.github.io/nq/PackageInfo.g ...
#I  The newest version of package "nq" is already installed
#I  Package ``nq'': The executable program is not available
#I  Package ``nq'': The executable program is not available
#I  Running compilation script on /Users/mhorn/.julia/gaproot/v4.13/pkg/nq-2.5.11/ ...
#I  Possible error detected, see log:
#I    + GAPROOT=/Users/mhorn/.julia/scratchspaces/c863536a-3901-11e9-33e7-d5cd0df7b904/gap_7216319432009064789_1.11
#I    + PKGDIR=/Users/mhorn/.julia/gaproot/v4.13/pkg/nq-2.5.11/
#I    + command -v gmake
...
+ ./configure --with-gaproot=/Users/mhorn/.julia/scratchspaces/c863536a-3901-11e9-33e7-d5cd0df7b904/gap_7216319432009064789_1.11
checking for a BSD-compatible install... /opt/homebrew/bin/ginstall -c
checking whether build environment is sane... yes
checking for a race-free mkdir -p... /opt/homebrew/bin/gmkdir -p
checking for gawk... no
...
checking for strings.h... yes
checking for sys/stat.h... yes
checking for sys/types.h... yes
checking for unistd.h... yes
checking for gmp.h... no
configure: error: Could not locate GMP, the GNU multiprecision library

#I  Package ``nq'': The executable program is not available
#I  Package ``nq'': The executable program is not available
#I  Checking dependencies for nq...
#I    polycyclic 2.11: true
#I  Package ``nq'': The executable program is not available
#I  Package ``nq'': The executable program is not available
#I  Package availability test failed

I tried fixing this by modifying setup.jl to do this (after suitably implementing gmp_artifact_dir)

  sysinfo["GMP_PREFIX"] = gmp_artifact_dir()

This then builds, however the resulting nq executable does not run standalone on macOS (which is what I expected):

dyld[56596]: Library not loaded: '@rpath/libgmp.10.dylib'
  Referenced from: '/Users/mhorn/.julia/gaproot/v4.13/pkg/nq-2.5.11/bin/aarch64-apple-darwin20-julia1.11-64-kv9/nq'
  Reason: tried: '/usr/local/lib/libgmp.10.dylib' (no such file), '/usr/lib/libgmp.10.dylib' (no such file)
Abort trap: 6

Perhaps I can fix this by ensuring the nq executable gets a suitable @rpath definition embedded... gotta play with LDFLAGS etc. (and then make sure I can pass them on to the nq build system... huh).

Of course the real plan is still to use JLLs to deal with this issue (instead of running a C compiler); however the binaries in the JLL will actually have the same issue. So we may need to also use BinaryWrappers.jl (in either GAP_pkg_nq.jl, or GAP.jl, or even both?!?)