Add clang_verify property for cc.

This property is to support cflags "-Xclang -verify" build pass in Soong. The behaviors of clang_verify:
- append cflags "-Xclang -verify"
- append "&& touch $out" to the clang command line

Bug: 311284462
Test: go test -run TestClangVerify

Change-Id: Ic5825e2d649da4c3c5ed6da916e9804d7e3c03da

cc/cc.go

@@ -260,6 +260,7 @@ type Flags struct {
 	GcovCoverage  bool // True if coverage files should be generated.
 	SAbiDump      bool // True if header abi dumps should be generated.
 	EmitXrefs     bool // If true, generate Ninja rules to generate emitXrefs input files for Kythe
+	ClangVerify   bool // If true, append cflags "-Xclang -verify" and append "&& touch $out" to the clang command line.
 
 	// The instruction set required for clang ("arm" or "thumb").
 	RequiredInstructionSet string