Memory mapped coverage (take 2)

Add a build variable, CLANG_COVERAGE_CONTINUOUS_MODE, instead of
selecting based on paths.

Test: CLANG_COVERAGE_CONTINUOUS_MODE=true m and verify continuous mode works

Change-Id: I731172fc1f00e1cabff8efcf8b99f9a48210b446
diff --git a/android/variable.go b/android/variable.go
index 68f19b9..37037eb 100644
--- a/android/variable.go
+++ b/android/variable.go
@@ -306,10 +306,11 @@
 	JavaCoveragePaths        []string `json:",omitempty"`
 	JavaCoverageExcludePaths []string `json:",omitempty"`
 
-	GcovCoverage               *bool    `json:",omitempty"`
-	ClangCoverage              *bool    `json:",omitempty"`
-	NativeCoveragePaths        []string `json:",omitempty"`
-	NativeCoverageExcludePaths []string `json:",omitempty"`
+	GcovCoverage                *bool    `json:",omitempty"`
+	ClangCoverage               *bool    `json:",omitempty"`
+	NativeCoveragePaths         []string `json:",omitempty"`
+	NativeCoverageExcludePaths  []string `json:",omitempty"`
+	ClangCoverageContinuousMode *bool    `json:",omitempty"`
 
 	// Set by NewConfig
 	Native_coverage *bool `json:",omitempty"`