rgdal and sf R packages fail to build on nixpkgs unstable

[cfhammill]

Describe the bug

The two R packages fail during the configure phase, pointing to inability to include the PROJ library

To Reproduce

nix-shell --packages "rPackages.rgdal"

and

nix-shell --packages "rPackages.sf"

tail output:

checking for gdal.h... yes
checking GDAL: linking with --libs only... yes
checking GDAL: /nix/store/kx0ck0m310dzakkbi7556ml2c25cgs4c-gdal-3.0.1/share/gdal/pcs.csv readable... no
checking GDAL: checking whether PROJ is available for linking:... yes
checking GDAL: checking whether PROJ is available fur running:... yes
checking proj_api.h usability... no
checking proj_api.h presence... no
checking for proj_api.h... no
configure: error: proj_api.h not found in standard or given locations.
ERROR: configuration failed for package 'sf'
* removing '/nix/store/4b8hhwbg5l6nhglar7jbf41rxyk9qrc2-r-sf-0.7-7/library/sf'
builder for '/nix/store/sznpd3bfjj5vlwy2d0hx4gjlqprrg1ba-r-sf-0.7-7.drv' failed with exit code 1
error: build of '/nix/store/sznpd3bfjj5vlwy2d0hx4gjlqprrg1ba-r-sf-0.7-7.drv' failed

Expected behavior

It should build

Metadata
Please run nix run nixpkgs.nix-info -c nix-info -m and paste the result.

 - system: `"x86_64-linux"`
 - host os: `Linux 4.13.0-46-generic, Ubuntu, 17.10 (Artful Aardvark)`
 - multi-user?: `no`
 - sandbox: `yes`
 - version: `nix-env (Nix) 2.2.2`
 - channels(chammill): `"nixpkgs-19.09pre190327.54f385241e6"`
 - nixpkgs: `/home/chammill/.nix-defexpr/channels/nixpkgs`

Maintainer information:

rPackages.sf
rPackages.rgdal

[stale]

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[cfhammill]

This was fixed with pull #67948