configure: handle mipsisa64* triplet as a mips64 target
the gnu config.sub script recognizes several mipsisa64* cpu types
that musl supports as mips64 targets.
diff --git a/configure b/configure
index af8b45f..707eb12 100755
--- a/configure
+++ b/configure
@@ -318,7 +318,7 @@
x86_64-x32*|x32*|x86_64*x32) ARCH=x32 ;;
x86_64-nt64*) ARCH=nt64 ;;
x86_64*) ARCH=x86_64 ;;
-mips64*) ARCH=mips64 ;;
+mips64*|mipsisa64*) ARCH=mips64 ;;
mips*) ARCH=mips ;;
microblaze*) ARCH=microblaze ;;
or1k*) ARCH=or1k ;;