Add support for LINE_COVERAGE (1/2)

This is the 1st part of the CL. It adds support to enable compilation
of line coverage instrumented binaries. For more details please refer
to the design doc: go/android-line-coverage-doc

Bug: b/147604881
Test: Code works successfully on Taimen devices
Change-Id: I07745c1438b611041ed032dd4b7788cb50130845
diff --git a/android/variable.go b/android/variable.go
index c277acc..9625a87 100644
--- a/android/variable.go
+++ b/android/variable.go
@@ -252,6 +252,7 @@
 	ClangTidy  *bool   `json:",omitempty"`
 	TidyChecks *string `json:",omitempty"`
 
+	NativeLineCoverage   *bool    `json:",omitempty"`
 	Native_coverage      *bool    `json:",omitempty"`
 	ClangCoverage        *bool    `json:",omitempty"`
 	CoveragePaths        []string `json:",omitempty"`