add support for Webassembly OS/arch

WebGHC uses the target 'triple' wasm32-unknown-unknown-wasm. While
aclocal.m4 already does have some provisions for wasm32, it and
config.sub need changes for successful build configuration when
cross-compiling GHC to target WebAssembly.
We would expect similar changes to eventually be made in upstream GNU
aclocal.m4 and config.sub.

Author: mvogelsang

aclocal.m4

@@ -217,7 +217,7 @@ AC_DEFUN([FPTOOLS_SET_HASKELL_PLATFORM_VARS],
         mipsel)
             test -z "[$]2" || eval "[$]2=ArchMipsel"
             ;;
-        hppa|hppa1_1|ia64|m68k|nios2|rs6000|s390|s390x|sh4|vax)
+        hppa|hppa1_1|ia64|m68k|nios2|rs6000|s390|s390x|sh4|vax|wasm32)
             test -z "[$]2" || eval "[$]2=ArchUnknown"
             ;;
         *)
@@ -272,7 +272,7 @@ AC_DEFUN([FPTOOLS_SET_HASKELL_PLATFORM_VARS],
         nto-qnx)
             test -z "[$]2" || eval "[$]2=OSQNXNTO"
             ;;
-        dragonfly|hpux|linuxaout|freebsd2|nextstep2|nextstep3|sunos4|ultrix)
+        dragonfly|hpux|linuxaout|freebsd2|nextstep2|nextstep3|sunos4|ultrix|unknown-wasm)
             test -z "[$]2" || eval "[$]2=OSUnknown"
             ;;
         aix)
@@ -1902,6 +1902,9 @@ case "$1" in
   x86_64|amd64)
     $2="x86_64"
     ;;
+  wasm32)
+    $2="wasm32"
+    ;;
   *)
     echo "Unknown CPU $1"
     exit 1
@@ -2009,6 +2012,9 @@ AC_DEFUN([GHC_CONVERT_OS],[
       nto-qnx*)
         $3="nto-qnx"
         ;;
+      unknown-wasm)
+        $3="unknown-wasm"
+        ;;
       *)
         echo "Unknown OS $1"
         exit 1

config.sub

@@ -118,7 +118,7 @@ case $maybe_os in
   linux-musl* | linux-uclibc* | uclinux-uclibc* | uclinux-gnu* | kfreebsd*-gnu* | \
   knetbsd*-gnu* | netbsd*-gnu* | netbsd*-eabi* | \
   kopensolaris*-gnu* | cloudabi*-eabi* | \
-  storm-chaos* | os2-emx* | rtmk-nova*)
+  storm-chaos* | os2-emx* | rtmk-nova* | unknown-wasm)
     os=-$maybe_os
     basic_machine=`echo $1 | sed 's/^\(.*\)-\([^-]*-[^-]*\)$/\1/'`
     ;;
@@ -1551,6 +1551,8 @@ case $os in
 		;;
 	-ios)
 		;;
+	-unknown-wasm)
+		;;
 	-none)
 		;;
 	*)