Bug 1661126 - Update wasi-sdk to pick up clang-11 build fixes r=firefox-build-system-reviewers,rstewart

Also reflects the move from CraneStation to the WebAssembly account. And we need a small tweak to the build script to accommodate one of the changes that got picked up along the way.

Differential Revision: https://phabricator.services.mozilla.com/D88187

taskcluster/ci/fetch/toolchains.yml

@@ -436,8 +436,8 @@ wasi-sdk:
     description: wasi-sdk source code
     fetch:
         type: git
-        repo: https://github.com/CraneStation/wasi-sdk
-        revision: 5225b05436ce57f01fe649f411f3ff701246628b
+        repo: https://github.com/WebAssembly/wasi-sdk
+        revision: 8446a3f8d49f70d17e38cefd9990a9e79bf3e78a
 
 ninja:
     description: ninja 1.9.0

taskcluster/scripts/misc/build-wasi-sysroot.sh

@@ -9,4 +9,4 @@ LLVM_PROJ_DIR=$MOZ_FETCHES_DIR/llvm-project
 make LLVM_PROJ_DIR=$LLVM_PROJ_DIR PREFIX=$PREFIX
 # Put a tarball in the artifacts dir
 mkdir -p $UPLOAD_DIR
-tar -C $MOZ_FETCHES_DIR/wasi-sdk/ -caf $UPLOAD_DIR/wasi-sysroot.tar.xz wasi-sysroot
+tar -C $MOZ_FETCHES_DIR/wasi-sdk/build/install/$PREFIX/../ -caf $UPLOAD_DIR/wasi-sysroot.tar.xz wasi-sysroot