fix toUpperCase without locale call

Author: chicobento

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/config/StandardConfigDataReference.java

@@ -16,6 +16,8 @@
 
 package org.springframework.boot.context.config;
 
+import java.util.Locale;
+
 import org.springframework.boot.env.PropertySourceLoader;
 import org.springframework.util.StringUtils;
 
@@ -52,7 +54,7 @@ class StandardConfigDataReference {
 			String extension, PropertySourceLoader propertySourceLoader) {
 		this.configDataLocation = configDataLocation;
 		String profileSuffix = (StringUtils.hasText(profile))
-				? root.startsWith("env:") ? "_" + profile.toUpperCase() : "-" + profile : "";
+				? root.startsWith("env:") ? "_" + profile.toUpperCase(Locale.ROOT) : "-" + profile : "";
 		this.resourceLocation = root + profileSuffix + ((extension != null) ? "." + extension : "");
 		this.directory = directory;
 		this.profile = profile;