Add CLANG_COVERAGE build flag to soong config.

Bug: 143977934
Test: m CLANG_COVERAGE=true
Change-Id: Ief6302a1724a9e8d5bd1a48ded4eb7d15ddf18de
diff --git a/core/soong_config.mk b/core/soong_config.mk
index 7ce59f1..232f3ef 100644
--- a/core/soong_config.mk
+++ b/core/soong_config.mk
@@ -113,6 +113,7 @@
 $(call add_json_str,  TidyChecks,                        $(WITH_TIDY_CHECKS))
 
 $(call add_json_bool, NativeCoverage,                    $(filter true,$(NATIVE_COVERAGE)))
+$(call add_json_bool, ClangCoverage,                     $(filter true,$(CLANG_COVERAGE)))
 $(call add_json_list, CoveragePaths,                     $(COVERAGE_PATHS))
 $(call add_json_list, CoverageExcludePaths,              $(COVERAGE_EXCLUDE_PATHS))