Add `HAVE_STDBOOL_H` define for Alberta when `stdbool.h` is available

In older versions of Alberta, it tries to fix the issues around not having proper bool in C by redefining bool as _Bool. Clang's stdbool header defines _Bool as bool, which then leads to a typedef bool bool and that gives a compile error. This whole bool/_Bool logic is inside an ifdef in Alberta that is only active if HAVE_STDBOOL_H is not defined. If HAVE_STDBOOL_H is defined, however, it just includes stdbool.h and uses that. So we can check during CMake configuration if stdbool.h is available and set the flag accordingly.

cmake/modules/FindAlberta.cmake

@@ -109,8 +109,21 @@ find_package_handle_standard_args("Alberta"
 )
 
 if(Alberta_FOUND)
+
+  if(ALBERTA_GRID_VERSION VERSION_LESS 3.1.0)
+    unset(HAVE_STDBOOL_H_HEADER)
+    include(CheckIncludeFileCXX)
+    check_include_file_cxx("stdbool.h" HAVE_STDBOOL_H_HEADER)
+  endif()
+
   foreach(dim ${ALBERTA_WORLD_DIMS})
     if(NOT Alberta::AlbertaGrid${dim}D)
+      if (${HAVE_STDBOOL_H_HEADER})
+         # Tell Alberta(<3.1.0) that we have a stdbool.h header so that it doesn't
+         # try to define `bool` itself (which would lead to a `typedef bool bool`
+         # and hence a compile error in clang).
+         target_compile_definitions(PkgConfig::Alberta${dim}D INTERFACE -DHAVE_STDBOOL_H)
+      endif()
       add_library(Alberta::AlbertaGrid${dim}D ALIAS PkgConfig::Alberta${dim}D)
     endif()
   endforeach(dim)