Stop using DIST_DIR in Soong

We're only using it to distribute files in case of failure, which isn't
well supported currently, but can be handled for now by using the
DIST_DIR environment variable during the command execution.

This was at least one cause that we'd be re-running Soong during every
build server build, as the DIST_DIR values are unique.

Test: m dist
Change-Id: Ibd5e6b6c46695350de80b745bfb6a6aa685033a0

cc/builder.go

@@ -191,11 +191,8 @@ var (
 		func(ctx android.PackageRuleContext) blueprint.RuleParams {
 			// TODO(b/78139997): Add -check-all-apis back
 			commandStr := "($sAbiDiffer $allowFlags -lib $libName -arch $arch -o ${out} -new $in -old $referenceDump)"
-			distAbiDiffDir := android.PathForDist(ctx, "abidiffs")
 			commandStr += "|| (echo ' ---- Please update abi references by running $$ANDROID_BUILD_TOP/development/vndk/tools/header-checker/utils/create_reference_dumps.py -l ${libName} ----'"
-			if distAbiDiffDir.Valid() {
-				commandStr += " && (mkdir -p " + distAbiDiffDir.String() + " && cp ${out} " + distAbiDiffDir.String() + ")"
-			}
+			commandStr += " && (mkdir -p $$DIST_DIR/abidiffs && cp ${out} $$DIST_DIR/abidiff/)"
 			commandStr += " && exit 1)"
 			return blueprint.RuleParams{
 				Command:     commandStr,