Generate "current" API level.

Support for using this coming in an upcoming patch.

Test: nose2
      readelf to check the following:
      * bsd_signal unversioned before current
      * bsd_signal versioned in current
      * catclose missing before current
      * catclose present and versioned in current
Bug: None
Change-Id: I861862161426d3ec5b530e3156d3a8ae96fed468
diff --git a/cc/ndk_library.go b/cc/ndk_library.go
index 94be17c..d603ad0 100644
--- a/cc/ndk_library.go
+++ b/cc/ndk_library.go
@@ -88,7 +88,7 @@
 	First_version string
 
 	// Private property for use by the mutator that splits per-API level.
-	ApiLevel int `blueprint:"mutated"`
+	ApiLevel string `blueprint:"mutated"`
 }
 
 type stubDecorator struct {
@@ -147,14 +147,15 @@
 		mctx.PropertyErrorf("first_version", err.Error())
 	}
 
-	versionStrs := make([]string, maxVersion-firstVersion+1)
+	var versionStrs []string
 	for version := firstVersion; version <= maxVersion; version++ {
-		versionStrs[version-firstVersion] = strconv.Itoa(version)
+		versionStrs = append(versionStrs, strconv.Itoa(version))
 	}
+	versionStrs = append(versionStrs, "current")
 
 	modules := mctx.CreateVariations(versionStrs...)
 	for i, module := range modules {
-		module.(*Module).compiler.(*stubDecorator).properties.ApiLevel = firstVersion + i
+		module.(*Module).compiler.(*stubDecorator).properties.ApiLevel = versionStrs[i]
 	}
 }
 
@@ -188,7 +189,7 @@
 			ndkLibrarySuffix)
 	}
 	libName := strings.TrimSuffix(ctx.ModuleName(), ndkLibrarySuffix)
-	fileBase := fmt.Sprintf("%s.%s.%d", libName, arch, c.properties.ApiLevel)
+	fileBase := fmt.Sprintf("%s.%s.%s", libName, arch, c.properties.ApiLevel)
 	stubSrcName := fileBase + ".c"
 	stubSrcPath := android.PathForModuleGen(ctx, stubSrcName)
 	versionScriptName := fileBase + ".map"
@@ -201,7 +202,7 @@
 		Input:   symbolFilePath,
 		Args: map[string]string{
 			"arch":     arch,
-			"apiLevel": strconv.Itoa(c.properties.ApiLevel),
+			"apiLevel": c.properties.ApiLevel,
 		},
 	})
 
@@ -252,7 +253,7 @@
 	}
 
 	installDir := getNdkInstallBase(ctx).Join(ctx, fmt.Sprintf(
-		"platforms/android-%d/arch-%s/usr/%s", apiLevel, arch, libDir))
+		"platforms/android-%s/arch-%s/usr/%s", apiLevel, arch, libDir))
 	stub.installPath = ctx.InstallFile(installDir, path).String()
 }