ci: extract install steps in its own action

.github/actions/install/action.yml

@@ -0,0 +1,49 @@
+name: "Browsercore install"
+description: "Install deps for the project browsercore"
+
+runs:
+  using: "composite"
+
+  steps:
+    - name: install v8
+      shell: bash
+      run: |
+        mkdir -p vendor/jsruntime-lib/vendor/v8/${{env.ARCH}}/debug
+        ln -s /usr/local/lib/libc_v8.a vendor/jsruntime-lib/vendor/v8/${{env.ARCH}}/debug/libc_v8.a
+
+        mkdir -p vendor/jsruntime-lib/vendor/v8/${{env.ARCH}}/release
+        ln -s /usr/local/lib/libc_v8.a vendor/jsruntime-lib/vendor/v8/${{env.ARCH}}/release/libc_v8.a
+
+    - name: install deps
+      shell: bash
+      run: |
+        ln -s /usr/local/lib/libiconv vendor/libiconv
+
+        ln -s /usr/local/lib/netsurf/build vendor/netsurf/build
+        ln -s /usr/local/lib/netsurf/lib vendor/netsurf/lib
+        ln -s /usr/local/lib/netsurf/include vendor/netsurf/include
+
+    # detect file change
+    - uses: dorny/paths-filter@v3.0.2
+      id: changes
+      with:
+        filters: |
+          netsurf:
+            - 'vendor/netsurf/**'
+
+    # if a vendor has changed, install build dependencies.
+    - name: install build dependencies
+      if: steps.changes.outputs.netsurf == 'true'
+      shell: bash
+      run: |
+        apt update && \
+        apt install -y git curl bash xz-utils python3 ca-certificates pkg-config \
+        libglib2.0-dev gperf libexpat1-dev cmake build-essential
+
+    # if netsurf has changed, force a rebuild.
+    - name: re-build netsurf
+      if: steps.changes.outputs.netsurf == 'true'
+      shell: bash
+      run: |
+        make clean-netsurf
+        make install-netsurf