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/config.go b/android/config.go
index 3d8bc31..e8ca84c 100644
--- a/android/config.go
+++ b/android/config.go
@@ -1256,6 +1256,10 @@
 	return Bool(c.config.productVariables.ClangCoverage)
 }
 
+func (c *deviceConfig) ClangCoverageContinuousMode() bool {
+	return Bool(c.config.productVariables.ClangCoverageContinuousMode)
+}
+
 func (c *deviceConfig) GcovCoverageEnabled() bool {
 	return Bool(c.config.productVariables.GcovCoverage)
 }