Use setup-emsdk instead of emscripten dockerfile in samples.yml. (#18422

)

Also delete the now unused `emscripten.Dockerfile` (it's technically
still referenced in a commented out `cross_compile_and_test` build, but
that can be added back as needed using this same technique).

Progress on #15332 - one less
Dockerfile to maintain.

Tested here:
https://github.com/ScottTodd/iree/actions/runs/10691087132/job/29636852886
(this samples.yml workflow runs on a nightly schedule).

skip-ci: no impact on other workflows

.github/workflows/samples.yml

@@ -61,7 +61,6 @@ jobs:
 
   web:
     runs-on: ubuntu-20.04
-    container: gcr.io/iree-oss/emscripten@sha256:2dd4c52f1bb499ab365aad0111fe5538b685d88af38636b409b0cf6a576ab214
     env:
       VENV_DIR: ${{ github.workspace }}/.venv
     defaults:
@@ -74,6 +73,12 @@ jobs:
         run: git config --global --add safe.directory '*'
       - name: "Check out runtime submodules"
         run: ./build_tools/scripts/git/update_runtime_submodules.sh
+      - name: "Installing build dependencies"
+        run: |
+          sudo apt update
+          sudo apt install -y ninja-build
+          echo "CC=clang" >> $GITHUB_ENV
+          echo "CXX=clang++" >> $GITHUB_ENV
       - uses: actions/setup-python@v5.1.0
         with:
           python-version: "3.11"
@@ -86,6 +91,10 @@ jobs:
             --upgrade \
             iree-compiler \
             iree-runtime
+      - name: "Setup emsdk"
+        uses: mymindstorm/setup-emsdk@v14
+        with:
+          version: 3.1.44
       - name: "Test experimental web samples"
         env:
           HOST_TOOLS_BINARY_DIR: ${{ env.VENV_DIR }}/bin

build_tools/docker/manage_images.py

@@ -45,7 +45,6 @@
 IMAGES_TO_DEPENDENCIES = {
     "base": [],
     "base-arm64": [],
-    "emscripten": ["base"],
     "riscv-toolchain-builder": [],
     # Containers with all the newest versions of dependencies that we support
     # instead of the oldest.

build_tools/docker/prod_digests.txt

@@ -1,5 +1,4 @@
 gcr.io/iree-oss/base@sha256:dc314b4fe30fc1315742512891357bffed4d1b62ffcb46258b1e0761c737b446
-gcr.io/iree-oss/emscripten@sha256:2dd4c52f1bb499ab365aad0111fe5538b685d88af38636b409b0cf6a576ab214
 gcr.io/iree-oss/base-bleeding-edge@sha256:cf2e78194e64fd0166f4141317366261d7a62432b72e9a324cb8c2ff4e1a515a
 gcr.io/iree-oss/base-arm64@sha256:9daa1cdbbf12da8527319ece76a64d06219e04ecb99a4cff6e6364235ddf6c59
 gcr.io/iree-oss/riscv-toolchain-builder@sha256:4240a374d35e5ea9037051559aaae4a8b6414ad5872501d4e240baccaacfff11