Drop ART_MODULE_BUILD_FROM_SOURCE

RELEASE_APEX_CONTRIBUTIONS_ART provides a similar functionality, and
also allows selection of a specific art prebuilt if multiple art
prebuilts exists in the tree

`art_module.source_build` was also previously used to conditionally
disable the source soong modules of art/, but this conditional disabling
has been removed with r.android.com/3045792

Bug: 308188056
Test: presubmits
Test: lunch cf_x86_64_phone-trunk_staging-userdebug; mmma art
Test: git_master-art:art-host-x86_64,art-target-arm64,mainline_modules
https://android-build.corp.google.com/builds/abtd/run/L30200030003163172
Test: git_master-art-host:art-build,art-gtest,art-test,art-preopt
https://android-build.corp.google.com/builds/abtd/run/L07600030003164399

Change-Id: Idbb129d2ec304d5320754cd61d40e10e5c7d5414
diff --git a/core/android_soong_config_vars.mk b/core/android_soong_config_vars.mk
index 56da574..18d245c 100644
--- a/core/android_soong_config_vars.mk
+++ b/core/android_soong_config_vars.mk
@@ -59,17 +59,6 @@
   MODULE_BUILD_FROM_SOURCE := $(BRANCH_DEFAULT_MODULE_BUILD_FROM_SOURCE)
 endif
 
-ifneq (,$(ART_MODULE_BUILD_FROM_SOURCE))
-  # Keep an explicit setting.
-else ifneq (,$(findstring .android.art,$(TARGET_BUILD_APPS)))
-  # Build ART modules from source if they are listed in TARGET_BUILD_APPS.
-  ART_MODULE_BUILD_FROM_SOURCE := true
-else
-  # Do the same as other modules by default.
-  ART_MODULE_BUILD_FROM_SOURCE := $(MODULE_BUILD_FROM_SOURCE)
-endif
-
-$(call soong_config_set,art_module,source_build,$(ART_MODULE_BUILD_FROM_SOURCE))
 ifdef ART_DEBUG_OPT_FLAG
 $(call soong_config_set,art_module,art_debug_opt_flag,$(ART_DEBUG_OPT_FLAG))
 endif