Add tempPathForRestat to improve consistency

Previously, there were two approaches used to construct the temporary
path needed by the commitChangeForRestat method and neither was
suitable for general use. One was:
    android.PathForOutput(ctx, outputPath.Rel()+".tmp")
The other was:
    combinedAidl.ReplaceExtension(ctx, "aidl.tmp")

The first approach would not work if the supplied path had been created
by PathForModuleOut() or similar as it would drop the module directory.
That could lead to the same path being used for multiple rules.

The second approach would not work for files with a different
extension.

The tempPathForRestat combines the two approaches so it can be used
generally with any WritablePath.

Bug: 179354495
Test: verified that the ninja rules that used these files were not
      changed by these changes.
Change-Id: I4439dea0a823512c281eeb1366522fb49dceb4e3

java/hiddenapi_singleton.go

@@ -15,6 +15,8 @@
 package java
 
 import (
+	"strings"
+
 	"android/soong/android"
 )
 
@@ -242,7 +244,7 @@ func stubFlagsRule(ctx android.SingletonContext) {
 	rule := android.NewRuleBuilder(pctx, ctx)
 
 	outputPath := hiddenAPISingletonPaths(ctx).stubFlags
-	tempPath := android.PathForOutput(ctx, outputPath.Rel()+".tmp")
+	tempPath := tempPathForRestat(ctx, outputPath)
 
 	rule.MissingDeps(missingDeps)
 
@@ -348,6 +350,16 @@ func emptyFlagsRule(ctx android.SingletonContext) android.Path {
 	return outputPath
 }
 
+// tempPathForRestat creates a path of the same type as the supplied type but with a name of
+// <path>.tmp.
+//
+// e.g. If path is an OutputPath for out/soong/hiddenapi/hiddenapi-flags.csv then this will return
+// an OutputPath for out/soong/hiddenapi/hiddenapi-flags.csv.tmp
+func tempPathForRestat(ctx android.PathContext, path android.WritablePath) android.WritablePath {
+	extWithoutLeadingDot := strings.TrimPrefix(path.Ext(), ".")
+	return path.ReplaceExtension(ctx, extWithoutLeadingDot+".tmp")
+}
+
 // commitChangeForRestat adds a command to a rule that updates outputPath from tempPath if they are different.  It
 // also marks the rule as restat and marks the tempPath as a temporary file that should not be considered an output of
 // the rule.