diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
new file mode 100644
index 000000000..6ca3845d4
--- /dev/null
+++ b/.github/workflows/main.yml
@@ -0,0 +1,133 @@
+name: main
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  build-core:
+    runs-on: ubuntu-latest
+    env:
+      EMSDK_NUM_CORES: 3
+      EMCC_CORES: 3
+      PYODIDE_JOBS: 3
+      CCACHE_DIR: /tmp/ccache
+
+    steps:
+      - uses: actions/checkout@v2
+
+      - name: Cache ccache output
+        uses: actions/cache@v2
+        with:
+          path: |
+            /tmp/ccache
+          key: ${{ hashFiles('Makefile.envs') }}-v20211025-
+
+      - uses: conda-incubator/setup-miniconda@v2
+        with:
+          activate-environment: pyodide-env
+          python-version: 3.9.5
+          channels: conda-forge
+
+      - name: Check Python versions
+        shell: bash -l {0}
+        run: |
+          python --version
+          which python
+
+      - name: Install dependencies
+        shell: bash -l {0}
+        run: |
+          sudo apt install -y build-essential git
+          conda install -y nodejs ccache f2c pkg-config swig make patch pkg-config texinfo autoconf automake libtool
+          pip install -r requirements.txt
+
+      - name: Build emsdk
+        shell: bash -l {0}
+        run: |
+          which ccache
+
+          ccache -z
+          make -C emsdk
+          ccache -s
+
+      - name: Build Cpython
+        shell: bash -l {0}
+        run: |
+          # This is necessary to use the ccache from emsdk
+          source pyodide_env.sh
+
+          which ccache
+
+          ccache -z
+          make -C cpython
+          ccache -s
+
+      - name: build Pyodide core + numpy
+        shell: bash -l {0}
+        run: |
+          # This is necessary to use the ccache from emsdk
+          source pyodide_env.sh
+          ccache -z
+          PYODIDE_PACKAGES="core,numpy" make
+          ccache -s
+
+      - name: check-size
+        run: ls -lh build/
+
+      - name: Store artifacts build
+        uses: actions/upload-artifact@v2
+        with:
+          name: core-build
+          path: ./build/
+          retention-days: 60
+
+  test-core:
+    runs-on: ubuntu-latest
+    env:
+      DISPLAY: :99
+
+    needs: build-core
+    strategy:
+      matrix:
+        selenium_runner: [firefox]
+
+    steps:
+      - uses: actions/checkout@v2
+
+      - name: Download build artifact
+        uses: actions/download-artifact@v2
+        with:
+          name: core-build
+          path: ./build/
+
+      - uses: conda-incubator/setup-miniconda@v2
+        with:
+          activate-environment: pyodide-env
+          python-version: 3.9.5
+          channels: conda-forge
+
+      - name: install test requirements
+        shell: bash -l {0}
+        run: |
+          pip install -r requirements.txt
+
+      - name: run core tests
+        env:
+          SELENIUM_RUNNER: ${{ matrix.selenium_runner }}
+        shell: bash -l {0}
+        run: |
+          ls -lh
+          ls -lh build/
+          tools/pytest_wrapper.py src packages/micropip/ -v -k "${SELENIUM_RUNNER}"
+
+      - name: run package tests
+        env:
+          SELENIUM_RUNNER: ${{ matrix.selenium_runner }}
+        shell: bash -l {0}
+        run: |
+          ls -lh
+          ls -lh build/
+          tools/pytest_wrapper.py packages/test* packages/*/test* -v -k "numpy and not joblib and ${SELENIUM_RUNNER}"
diff --git a/conftest.py b/conftest.py
index ca19ea0bd..a06ce7988 100644
--- a/conftest.py
+++ b/conftest.py
@@ -300,7 +300,7 @@ class FirefoxWrapper(SeleniumWrapper):
         from selenium.webdriver.firefox.options import Options
 
         options = Options()
-        options.add_argument("-headless")
+        options.add_argument("--headless")
 
         return Firefox(executable_path="geckodriver", options=options)
 
diff --git a/pyodide-build/pyodide_build/pywasmcross.py b/pyodide-build/pyodide_build/pywasmcross.py
index 76181657b..997b84fd8 100755
--- a/pyodide-build/pyodide_build/pywasmcross.py
+++ b/pyodide-build/pyodide_build/pywasmcross.py
@@ -348,6 +348,10 @@ def handle_command(line, args, dryrun=False):
             del new_args[-1]
             continue
 
+        # ignore unsupported --sysroot compile argument used in conda
+        if arg.startswith("-Wl,--sysroot"):
+            continue
+
         # See https://github.com/emscripten-core/emscripten/issues/8650
         if arg in ["-lfreetype", "-lz", "-lpng", "-lgfortran"]:
             continue
diff --git a/pyodide-build/pyodide_build/tests/test_pywasmcross.py b/pyodide-build/pyodide_build/tests/test_pywasmcross.py
index 2ec4a20da..32c6dc6db 100644
--- a/pyodide-build/pyodide_build/tests/test_pywasmcross.py
+++ b/pyodide-build/pyodide_build/tests/test_pywasmcross.py
@@ -114,12 +114,18 @@ def test_f2c():
     )
 
 
-def test_conda_compiler_compat():
+def test_conda_unsupported_args():
+    # Check that compile arguments that are not suported by emcc and are sometimes
+    # used in conda are removed.
     args = BuildArgs()
     assert handle_command_wrap(
         "gcc -shared -c test.o -B /compiler_compat -o test.so", args
     ) == ("emcc -c test.o -o test.so")
 
+    assert handle_command_wrap(
+        "gcc -shared -c test.o -Wl,--sysroot=/ -o test.so", args
+    ) == ("emcc -c test.o -o test.so")
+
 
 def test_environment_var_substitution(monkeypatch):
     monkeypatch.setenv("PYODIDE_BASE", "pyodide_build_dir")