Remove USE_CLANG_LLD[=false]

This should always be true now. It will be a change for side branches
(build_tools, etc) that weren't setting UseClangLld in the
soong.variables file.

Test: treehugger
Change-Id: I9fd6157fda630bf8bb939677dbcb026f02685f19

android/config.go

@@ -646,10 +646,6 @@ func (c *config) TargetOpenJDK9() bool {
 	return c.targetOpenJDK9
 }
 
-func (c *config) UseClangLld() bool {
-	return Bool(c.productVariables.UseClangLld)
-}
-
 func (c *config) ClangTidy() bool {
 	return Bool(c.productVariables.ClangTidy)
 }

android/variable.go

@@ -201,8 +201,6 @@ type productVariables struct {
 	ProductPath         *string `json:",omitempty"`
 	ProductServicesPath *string `json:",omitempty"`
 
-	UseClangLld *bool `json:",omitempty"`
-
 	ClangTidy  *bool   `json:",omitempty"`
 	TidyChecks *string `json:",omitempty"`