Index: gcc-4.9.1/libstdc++-v3/configure.host
===================================================================
--- gcc-4.9.1.orig/libstdc++-v3/configure.host
+++ gcc-4.9.1/libstdc++-v3/configure.host
@@ -264,6 +264,13 @@ case "${host_os}" in
     os_include_dir="os/bsd/freebsd"
     ;;
   gnu* | linux* | kfreebsd*-gnu | knetbsd*-gnu)
+    # check for musl by target
+    case "${host_os}" in
+      *-musl*)
+        os_include_dir="os/generic"
+        ;;
+      *)
+
     if [ "$uclibc" = "yes" ]; then
       os_include_dir="os/uclibc"
     elif [ "$bionic" = "yes" ]; then
@@ -272,6 +279,9 @@ case "${host_os}" in
       os_include_dir="os/gnu-linux"
     fi
     ;;
+
+    esac
+    ;;
   hpux*)
     os_include_dir="os/hpux"
     ;;