Add C.utf8 to supported locales

Several Linux distros (e.g. Fedora) , use C.utf8 instead of C.UTF-8

Test: builds
Change-Id: I7e3dd73ec89bc34d7f2dc1834082cc90f9521ad1
diff --git a/ui/build/config.go b/ui/build/config.go
index eefe0ed..c171a67 100644
--- a/ui/build/config.go
+++ b/ui/build/config.go
@@ -293,6 +293,9 @@
 	// for others)
 	if inList("C.UTF-8", locales) {
 		c.environ.Set("LANG", "C.UTF-8")
+	} else if inList("C.utf8", locales) {
+		// These normalize to the same thing
+		c.environ.Set("LANG", "C.UTF-8")
 	} else if inList("en_US.UTF-8", locales) {
 		c.environ.Set("LANG", "en_US.UTF-8")
 	} else if inList("en_US.utf8", locales) {