title: Error installing R package sf 0.9.0 after updating gdal on macOS
body: <p>I've had <code>sf</code> and <code>rproj</code> working on mac forever, and still working since upgrading to Catalina / R 3.6.2. </p>
  
  <p>I tried to install the latest version of <code>sf</code> (0.9.0), both from CRAN and the dev version, and get errors both ways, <code>configure: error: libproj not found in standard or given locations.</code></p>
  
  <p>I've gone through and removed every last trace of gdal and proj on my computer, uninstalled both, reinstalled, and still same issue. And now, trying to install older versions of <code>sf</code> (0.8.1) that I know worked on my computer also fails. Absolutely stumped here!</p>
  
  <p>GDAL 2.4.4, released 2020/01/08</p>
  
  <p>R v3.6.2</p>
  
  <p>macOS 10.15.3</p>
  
  <pre><code>configure: CC: clang
  configure: CXX: clang++ -std=gnu++11
  checking for gdal-config... /usr/local/bin/gdal-config
  checking gdal-config usability... yes
  configure: GDAL: 2.4.4
  checking GDAL version &gt;= 2.0.1... yes
  checking for gcc... clang
  checking whether the C compiler works... yes
  checking for C compiler default output file name... a.out
  checking for suffix of executables... 
  checking whether we are cross compiling... no
  checking for suffix of object files... o
  checking whether we are using the GNU C compiler... yes
  checking whether clang accepts -g... yes
  checking for clang option to accept ISO C89... none needed
  checking how to run the C preprocessor... clang -E
  checking for grep that handles long lines and -e... /usr/bin/grep
  checking for egrep... /usr/bin/grep -E
  checking for ANSI C header files... yes
  checking for sys/types.h... yes
  checking for sys/stat.h... yes
  checking for stdlib.h... yes
  checking for string.h... yes
  checking for memory.h... yes
  checking for strings.h... yes
  checking for inttypes.h... yes
  checking for stdint.h... yes
  checking for unistd.h... yes
  checking gdal.h usability... yes
  checking gdal.h presence... yes
  checking for gdal.h... yes
  checking GDAL: linking with --libs only... yes
  checking GDAL: /usr/local/Cellar/gdal/2.4.4_2/share/gdal/pcs.csv readable... yes
  checking GDAL: checking whether PROJ is available for linking:... yes
  checking GDAL: checking whether PROJ is available fur running:... yes
  configure: GDAL: 2.4.4
  checking proj.h usability... yes
  checking proj.h presence... yes
  checking for proj.h... yes
  checking PROJ: checking whether PROJ and sqlite3 are available for linking:... no
  configure: error: libproj not found in standard or given locations.
  </code></pre>
  
  <p>for <code>rgdal</code>...</p>
  
  <pre><code>* installing *source* package ‘rgdal’ ...
  ** package ‘rgdal’ successfully unpacked and MD5 sums checked
  ** using staged installation
  configure: R_HOME: /Library/Frameworks/R.framework/Resources
  configure: CC: clang
  configure: CXX: clang++ -std=gnu++11
  configure: C++11 support available
  configure: rgdal: 1.4-7
  checking for /usr/bin/svnversion... yes
  configure: svn revision: 845
  checking for gdal-config... /usr/local/bin/gdal-config
  checking gdal-config usability... yes
  configure: GDAL: 2.4.4
  checking C++11 support for GDAL &gt;= 2.3.0... yes
  checking GDAL version &gt;= 1.11.4... yes
  checking GDAL version &lt;= 2.5 or &gt;= 3.0... yes
  checking gdal: linking with --libs only... yes
  checking GDAL: gdal-config data directory readable... yes
  checking GDAL: /usr/local/Cellar/gdal/2.4.4_2/share/gdal/pcs.csv readable... yes
  configure: pkg-config proj not available
    set PKG_CONFIG_PATH to the directory containing proj.pc
  configure: PROJ version not determined using pkg-config proj
  configure: proj CPP flags:  -I/usr/local/Cellar/gdal/2.4.4_2/include
  configure: PROJ LIBS:  -lproj
  checking PROJ header API:... proj_api.h
  checking proj_api.h presence and usability... no
  configure: error: proj_api.h not found in standard or given locations.
  ERROR: configuration failed for package ‘rgdal’
  * removing ‘/Library/Frameworks/R.framework/Versions/3.6/Resources/library/rgdal
  </code></pre>