Avoid build-only store references embedding into 'mutt -v'.
--- a/txt2c.sh
+++ b/txt2c.sh
@@ -21,8 +21,18 @@ txt2c_fallback () {
 	echo ";"
 }
 
+nix_store_mangle() {
+	# consume stdin
+
+	# Avoid build-only references to nix store. These are usually
+	# 'gcc -v' output embedded into 'mutt -v'. But also might be
+	# ./configure-passed arguments.
+	sed \
+	    -e "s|$NIX_STORE/[a-z0-9]\{32\}-|$NIX_STORE/eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee-|g"
+}
+
 if ./txt2c test </dev/null >/dev/null 2>&1; then
-    ./txt2c "$1"
+    nix_store_mangle | ./txt2c "$1"
 else
-    txt2c_fallback "$1"
+    nix_store_mangle | txt2c_fallback "$1"
 fi