Set incremental or codegen-units, not both

This CL changes the handling of Rust flags to only pass one of either
incremental or codegen-units.  This is necessary because incremental
implies a codegen-units value of 128 and it may be overridden by the
separate codegen-units argument.

Test: TH
Change-Id: Ia474e4f9fc071d5054cb479ec9de550fa886677e

rust/builder.go

@@ -278,7 +278,9 @@ func transformSrctoCrate(ctx ModuleContext, main android.Path, deps PathDeps, fl
 	if ctx.Config().IsEnvTrue("SOONG_RUSTC_INCREMENTAL") {
 		incrementalPath := android.PathForOutput(ctx, "rustc").String()
 
-		rustcFlags = append(rustcFlags, "-Cincremental="+incrementalPath)
+		rustcFlags = append(rustcFlags, "-C incremental="+incrementalPath)
+	} else {
+		rustcFlags = append(rustcFlags, "-C codegen-units=1")
 	}
 
 	// Disallow experimental features

rust/config/global.go

@@ -44,7 +44,6 @@ var (
 	GlobalRustFlags = []string{
 		"-Z stack-protector=strong",
 		"-Z remap-cwd-prefix=.",
-		"-C codegen-units=1",
 		"-C debuginfo=2",
 		"-C opt-level=3",
 		"-C relocation-model=pic",
@@ -55,7 +54,7 @@ var (
 		// This flag requires to have no space so that when it's exported to bazel
 		// it can be removed. See aosp/2768339
 		"--color=always",
-		"-Zdylib-lto",
+		"-Z dylib-lto",
 		"-Z link-native-libraries=no",
 	}