Add explicit rspfile argument to RuleBuilderCommand.FlagWithRspFileInputList

Using $out.rsp as the rsp file adds extra complexity around keeping
the $ unescaped.  Make callers to FlagWithRspFileInputList provide
an explicit path for the rsp file instead.

Bug: 182612695
Test: rule_builder_test.go
Change-Id: I3f531d80c1efa8a9d09aac0a63790c5b11a9f0c6
diff --git a/genrule/genrule_test.go b/genrule/genrule_test.go
index d131e94..199a7df 100644
--- a/genrule/genrule_test.go
+++ b/genrule/genrule_test.go
@@ -298,6 +298,14 @@
 			`,
 			expect: "echo foo > __SBOX_SANDBOX_DIR__/out/foo && cp __SBOX_SANDBOX_DIR__/out/foo __SBOX_SANDBOX_DIR__/out/out",
 		},
+		{
+			name: "$",
+			prop: `
+				out: ["out"],
+				cmd: "echo $$ > $(out)",
+			`,
+			expect: "echo $ > __SBOX_SANDBOX_DIR__/out/out",
+		},
 
 		{
 			name: "error empty location",