Add coverage flags for Clang coverage builds.

Bug: 143977934
Test: m CLANG_COVERAGE=true
Test: m NATIVE_COVERAGE=true
Change-Id: I5d07d336e241856961eb0bc9678fdc9d5a076802
diff --git a/android/variable.go b/android/variable.go
index 25a5dc0..bcab46a 100644
--- a/android/variable.go
+++ b/android/variable.go
@@ -243,6 +243,7 @@
 	TidyChecks *string `json:",omitempty"`
 
 	NativeCoverage       *bool    `json:",omitempty"`
+	ClangCoverage        *bool    `json:",omitempty"`
 	CoveragePaths        []string `json:",omitempty"`
 	CoverageExcludePaths []string `json:",omitempty"`