mkarchiso: unset LANGUAGE

LC_ALL=C.UTF-8, unlike LC_ALL=C, does not override LANGUAGE.
See https://sourceware.org/bugzilla/show_bug.cgi?id=16621 and https://savannah.gnu.org/bugs/?62815

archiso/mkarchiso

@@ -7,6 +7,11 @@ set -e -u
 # Control the environment
 umask 0022
 export LC_ALL="C.UTF-8"
+if [[ -v LANGUAGE ]]; then
+    # LC_ALL=C.UTF-8, unlike LC_ALL=C, does not override LANGUAGE.
+    # See https://sourceware.org/bugzilla/show_bug.cgi?id=16621 and https://savannah.gnu.org/bugs/?62815
+    unset LANGUAGE
+fi
 [[ -v SOURCE_DATE_EPOCH ]] || printf -v SOURCE_DATE_EPOCH '%(%s)T' -1
 export SOURCE_DATE_EPOCH