FindGDAL: remove usage of gdal-config

CMake builds don't contain this tool and a CMake build gets shadowed by
the availability of a non-CMake build with it. Instead, just generate
the possible library names.

CMake/patches/99/FindGDAL.cmake

@@ -60,68 +60,6 @@ GDAL installation prefix.
 #
 #include "gdal.h"
 
-if(UNIX)
-    # Use gdal-config to obtain the library version (this should hopefully
-    # allow us to -lgdal1.x.y where x.y are correct version)
-    # For some reason, libgdal development packages do not contain
-    # libgdal.so...
-    find_program(GDAL_CONFIG gdal-config
-        HINTS
-          ${GDAL_ROOT}
-          ENV GDAL_DIR
-          ENV GDAL_ROOT
-        PATH_SUFFIXES bin
-    )
-
-    if(GDAL_CONFIG)
-        exec_program(${GDAL_CONFIG} ARGS --libs OUTPUT_VARIABLE GDAL_CONFIG_LIBS)
-
-        if(GDAL_CONFIG_LIBS)
-            # treat the output as a command line and split it up
-            separate_arguments(args NATIVE_COMMAND "${GDAL_CONFIG_LIBS}")
-
-            # only consider libraries whose name matches this pattern
-            set(name_pattern "[gG][dD][aA][lL]")
-
-            # consider each entry as a possible library path, name, or parent directory
-            foreach(arg IN LISTS args)
-                # library name
-                if("${arg}" MATCHES "^-l(.*)$")
-                    set(lib "${CMAKE_MATCH_1}")
-
-                    # only consider libraries whose name matches the expected pattern
-                    if("${lib}" MATCHES "${name_pattern}")
-                        list(APPEND _gdal_lib "${lib}")
-                    endif()
-                # library search path
-                elseif("${arg}" MATCHES "^-L(.*)$")
-                    list(APPEND _gdal_libpath "${CMAKE_MATCH_1}")
-                # assume this is a full path to a library
-                elseif(IS_ABSOLUTE "${arg}" AND EXISTS "${arg}")
-                    # extract the file name
-                    get_filename_component(lib "${arg}" NAME)
-
-                    # only consider libraries whose name matches the expected pattern
-                    if(NOT "${lib}" MATCHES "${name_pattern}")
-                        continue()
-                    endif()
-
-                    # extract the file directory
-                    get_filename_component(dir "${arg}" DIRECTORY)
-
-                    # remove library prefixes/suffixes
-                    string(REGEX REPLACE "^(${CMAKE_SHARED_LIBRARY_PREFIX}|${CMAKE_STATIC_LIBRARY_PREFIX})" "" lib "${lib}")
-                    string(REGEX REPLACE "(${CMAKE_SHARED_LIBRARY_SUFFIX}|${CMAKE_STATIC_LIBRARY_SUFFIX})$" "" lib "${lib}")
-
-                    # use the file name and directory as hints
-                    list(APPEND _gdal_libpath "${dir}")
-                    list(APPEND _gdal_lib "${lib}")
-                endif()
-            endforeach()
-        endif()
-    endif()
-endif()
-
 find_path(GDAL_INCLUDE_DIR gdal.h
   HINTS
     ${GDAL_ROOT}
@@ -133,18 +71,22 @@ find_path(GDAL_INCLUDE_DIR gdal.h
      include
 )
 
+# GDAL name its library when built with CMake as `gdal${major}${minor}`.
+set(_gdal_versions
+    3.0 2.4 2.3 2.2 2.1 2.0 1.11 1.10 1.9 1.8 1.7 1.6 1.5 1.4 1.3 1.2)
+
+set(_gdal_libnames)
+foreach (_gdal_version IN LISTS _gdal_versions)
+    string(REPLACE "." "" _gdal_version "${_gdal_version}")
+    list(APPEND _gdal_libnames "gdal${_gdal_version}" "GDAL${_gdal_libnames}")
+endforeach ()
+
 find_library(GDAL_LIBRARY
-  NAMES ${_gdal_lib} gdal gdal_i gdal1.5.0 gdal1.4.0 gdal1.3.2 GDAL
+  NAMES ${_gdal_libnames} gdal gdal_i gdal1.5.0 gdal1.4.0 gdal1.3.2 GDAL
   HINTS
      ${GDAL_ROOT}
      ENV GDAL_DIR
      ENV GDAL_ROOT
-     # This is last because `gdal-config` may not exist if it was built with
-     # CMake. Looking for it out-of-order with the include path may end up with
-     # a CMake-built include path and a autoconf-built libpath from the
-     # `gdal-config` tool.
-     ${_gdal_libpath}
-  PATH_SUFFIXES lib
 )
 
 if (EXISTS "${GDAL_INCLUDE_DIR}/gdal_version.h")