Add config/aom_config.h include dir only for AVM

config/aom_config.h is a private header, so public headers should not
include it. During AVM development, its public headers need to include
config/aom_config.h for the definitions of experiment macros. So add the
include directory for config/aom_config.h only for AVM.

cmake/Modules/LocalAom.cmake

diff --git a/cmake/Modules/LocalAom.cmake b/cmake/Modules/LocalAom.cmake
index 31a622f..4f10019 100644
--- a/cmake/Modules/LocalAom.cmake
+++ b/cmake/Modules/LocalAom.cmake
@@ -20,7 +20,7 @@
     set_target_properties(aom PROPERTIES IMPORTED_LOCATION "${LIB_FILENAME}" AVIF_LOCAL ON)
     target_include_directories(aom INTERFACE $<BUILD_INTERFACE:${AOM_EXT_SOURCE_DIR}>)
     if(AVIF_CODEC_AVM)
-        # ext/avm/aom/aom_encoder.h includes config/aom_config.h which is generated by the local build of avm.
+        # avm/aom/aom_encoder.h includes config/aom_config.h which is generated by the local build of avm.
         target_include_directories(aom INTERFACE $<BUILD_INTERFACE:${AOM_EXT_SOURCE_DIR}/build.libavif>)
     endif()
 
@@ -185,7 +185,11 @@
     endif()
 
     set_property(TARGET aom PROPERTY AVIF_LOCAL ON)
-    target_include_directories(aom INTERFACE $<BUILD_INTERFACE:$<PATH:ABSOLUTE_PATH,${libaom_SOURCE_DIR},/>;${AOM_BINARY_DIR}>)
+    target_include_directories(aom INTERFACE $<BUILD_INTERFACE:$<PATH:ABSOLUTE_PATH,${libaom_SOURCE_DIR},/>>)
+    if(AVIF_CODEC_AVM)
+        # avm/aom/aom_encoder.h includes config/aom_config.h which is generated by the local build of avm.
+        target_include_directories(aom INTERFACE $<BUILD_INTERFACE:${AOM_BINARY_DIR}>)
+    endif()
 
     message(CHECK_PASS "complete")
 endif()