Do not enforce using explicit build types. (#7376)

cmake_multi enforced existence of conanbuildinfo_release.cmake &
conanbuildinfo_debug.cmake had to be present or the build would fail if
conanbuildinfo_multi.cmake was loaded. This is now changed so that
only generated conanbuildinfo files are loaded.

Fixes #7253

conans/client/generators/cmake_common.py

@@ -971,25 +971,12 @@ def _conan_basic_setup_common(addtional_macros, cmake_multi=False):
 
 cmake_macros_multi = "\n".join([
     textwrap.dedent("""
-        if(EXISTS ${CMAKE_CURRENT_LIST_DIR}/conanbuildinfo_release.cmake)
-            include(${CMAKE_CURRENT_LIST_DIR}/conanbuildinfo_release.cmake)
-        else()
-            message(FATAL_ERROR "No conanbuildinfo_release.cmake, please install the Release conf first")
-        endif()
-
-        if(EXISTS ${CMAKE_CURRENT_LIST_DIR}/conanbuildinfo_debug.cmake)
-            include(${CMAKE_CURRENT_LIST_DIR}/conanbuildinfo_debug.cmake)
-        else()
-            message(FATAL_ERROR "No conanbuildinfo_debug.cmake, please install the Debug conf first")
-        endif()
-
-        if(EXISTS ${CMAKE_CURRENT_LIST_DIR}/conanbuildinfo_minsizerel.cmake)
-            include(${CMAKE_CURRENT_LIST_DIR}/conanbuildinfo_minsizerel.cmake)
-        endif()
-
-        if(EXISTS ${CMAKE_CURRENT_LIST_DIR}/conanbuildinfo_relwithdebinfo.cmake)
-            include(${CMAKE_CURRENT_LIST_DIR}/conanbuildinfo_relwithdebinfo.cmake)
-        endif()
+        ### load generated conanbuildinfo files.
+        foreach(_name release debug minsizerel relwithdebinfo)
+            if(EXISTS ${CMAKE_CURRENT_LIST_DIR}/conanbuildinfo_${_name}.cmake)
+                include(${CMAKE_CURRENT_LIST_DIR}/conanbuildinfo_${_name}.cmake)
+            endif()
+        endforeach()
         """),
     CMakeCommonMacros.conan_set_vs_runtime_preserve_build_type,
     CMakeCommonMacros.conan_set_find_paths_multi,