patch for Homebrew postgis formula to rely on gdal2

brew.info.json

[
  {
    "name": "gdal2",
    "full_name": "osgeo/osgeo4mac/gdal2",
    "desc": "GDAL: Geospatial Data Abstraction Library",
    "homepage": "http://www.gdal.org/",
    "oldname": null,
    "aliases": [
      "gdal-20"
    ],
    "versions": {
      "stable": "2.2.3",
      "bottle": true,
      "devel": null,
      "head": "HEAD"
    },
    "revision": 0,
    "version_scheme": 0,
    "installed": [
      {
        "version": "2.2.3",
        "used_options": [
          "--with-sfcgal",
          "--with-qhull",
          "--with-postgresql",
          "--with-mdb",
          "--with-armadillo"
        ],
        "built_as_bottle": false,
        "poured_from_bottle": false,
        "runtime_dependencies": [
          {
            "full_name": "libpng",
            "version": "1.6.34"
          },
          {
            "full_name": "jpeg",
            "version": "9b"
          },
          {
            "full_name": "giflib",
            "version": "5.1.4"
          },
          {
            "full_name": "libtiff",
            "version": "4.0.9"
          },
          {
            "full_name": "proj",
            "version": "4.9.3"
          },
          {
            "full_name": "libgeotiff",
            "version": "1.4.2"
          },
          {
            "full_name": "geos",
            "version": "3.6.2"
          },
          {
            "full_name": "sqlite",
            "version": "3.21.0"
          },
          {
            "full_name": "pcre",
            "version": "8.41"
          },
          {
            "full_name": "freexl",
            "version": "1.0.4"
          },
          {
            "full_name": "libspatialite",
            "version": "4.3.0a"
          },
          {
            "full_name": "openssl",
            "version": "1.0.2n"
          },
          {
            "full_name": "readline",
            "version": "7.0.3"
          },
          {
            "full_name": "postgresql",
            "version": "10.1"
          },
          {
            "full_name": "veclibfort",
            "version": "0.4.2"
          },
          {
            "full_name": "arpack",
            "version": "3.5.0"
          },
          {
            "full_name": "szip",
            "version": "2.1.1"
          },
          {
            "full_name": "hdf5",
            "version": "1.10.1"
          },
          {
            "full_name": "superlu",
            "version": "5.2.1"
          },
          {
            "full_name": "armadillo",
            "version": "8.300.3"
          },
          {
            "full_name": "boost",
            "version": "1.66.0"
          },
          {
            "full_name": "gmp",
            "version": "6.1.2"
          },
          {
            "full_name": "mpfr",
            "version": "3.1.6"
          },
          {
            "full_name": "cgal",
            "version": "4.11"
          },
          {
            "full_name": "sfcgal",
            "version": "1.3.2"
          },
          {
            "full_name": "gcc",
            "version": "7.2.0"
          }
        ],
        "installed_as_dependency": false,
        "installed_on_request": true
      }
    ],
    "linked_keg": null,
    "pinned": false,
    "outdated": false,
    "keg_only": true,
    "dependencies": [
      "libpng",
      "jpeg",
      "giflib",
      "libtiff",
      "libgeotiff",
      "proj",
      "geos",
      "sqlite",
      "pcre",
      "freexl",
      "libspatialite",
      "postgresql",
      "mysql",
      "ogdi",
      "armadillo",
      "sfcgal"
    ],
    "recommended_dependencies": [],
    "optional_dependencies": [
      "postgresql",
      "mysql",
      "ogdi",
      "armadillo",
      "sfcgal"
    ],
    "build_dependencies": [],
    "conflicts_with": [],
    "caveats": "Plugins for this version of GDAL/OGR, generated by other formulae, should\nbe symlinked to the following directory:\n\n  /usr/local/lib/gdalplugins/2.2\n\nYou may need to set the following enviroment variable:\n\n  export GDAL_DRIVER_PATH=/usr/local/lib/gdalplugins\n\nPYTHON BINDINGS are now built in a separate formula: gdal2-python\n",
    "requirements": [
      {
        "name": "java",
        "cask": "java",
        "download": "https://www.oracle.com/technetwork/java/javase/downloads/index.html"
      }
    ],
    "options": [
      {
        "option": "--with-complete",
        "description": "Use additional Homebrew libraries to provide more drivers."
      },
      {
        "option": "--with-qhull",
        "description": "Build with internal qhull libary support"
      },
      {
        "option": "--with-opencl",
        "description": "Build with OpenCL acceleration."
      },
      {
        "option": "--with-armadillo",
        "description": "Build with Armadillo accelerated TPS transforms."
      },
      {
        "option": "--with-unsupported",
        "description": "Allow configure to drag in any library it can find. Invoke this at your own risk."
      },
      {
        "option": "--with-mdb",
        "description": "Build with Access MDB driver (requires Java 1.6+ JDK/JRE, from Apple or Oracle)."
      },
      {
        "option": "--without-gnm",
        "description": "Build without Geographic Network Model support"
      },
      {
        "option": "--with-libkml",
        "description": "Build with Google's libkml driver (requires libkml-dev >= 1.3)"
      },
      {
        "option": "--with-swig-java",
        "description": "Build the swig java bindings"
      },
      {
        "option": "--with-sfcgal",
        "description": "Build with CGAL C++ wrapper support"
      },
      {
        "option": "--with-ogdi",
        "description": "Build with OGDI support (consider gdal2-ogdi instead)"
      },
      {
        "option": "--with-postgresql",
        "description": "Build with postgresql support"
      },
      {
        "option": "--with-mysql",
        "description": "Build with mysql support"
      },
      {
        "option": "--with-java",
        "description": "Build with java support"
      }
    ],
    "bottle": {
      "stable": {
        "rebuild": 0,
        "cellar": "/usr/local/Cellar",
        "prefix": "/usr/local",
        "root_url": "https://osgeo4mac.s3.amazonaws.com/bottles",
        "files": {
          "sierra": {
            "url": "https://osgeo4mac.s3.amazonaws.com/bottles/gdal2-2.2.3.sierra.bottle.tar.gz",
            "sha256": "4041b35db4dd7615cc8b90b2a7f3af0decfd4a9659af68673104d6c88f8326c9"
          },
          "high_sierra": {
            "url": "https://osgeo4mac.s3.amazonaws.com/bottles/gdal2-2.2.3.high_sierra.bottle.tar.gz",
            "sha256": "4041b35db4dd7615cc8b90b2a7f3af0decfd4a9659af68673104d6c88f8326c9"
          }
        }
      }
    }
  }
]

postgis.rb.patch

diff --git Formula/postgis.rb Formula/postgis.rb
index 6b300747..bd9b9fb3 100644
--- Formula/postgis.rb
+++ Formula/postgis.rb
@@ -36,8 +36,8 @@ class Postgis < Formula
 
   # For GeoJSON and raster handling
   depends_on "json-c"
-  depends_on "gdal" => :recommended
-  depends_on "pcre" if build.with? "gdal"
+  depends_on "osgeo/osgeo4mac/gdal2" => :recommended
+  depends_on "pcre" if build.with? "osgeo/osgeo4mac/gdal2"
 
   # For advanced 2D/3D functions
   depends_on "sfcgal" => :recommended