feat: Support running CI locally with `act`

Disable problematic jobs that involve Github Actions caching or `cross`
whenever the environment is set to ACT. This allows running the CI
pipeline locally and hopefully speeds up PR cycle times by reducing
unexpected CI pipeline results.

.actrc

@@ -0,0 +1 @@
+-e contrib/act/event.json

.github/workflows/fuzz.yml

@@ -5,6 +5,7 @@ on: [push, pull_request]
 jobs:
 
   fuzz:
+    if: ${{ !github.event.act }}
     runs-on: ubuntu-20.04
     env:
       HFUZZ_BUILD_ARGS: "--features honggfuzz_fuzz"
@@ -41,6 +42,7 @@ jobs:
           path: executed_${{ matrix.fuzz_target }}
 
   verify-execution:
+    if: ${{ !github.event.act }}
     needs: fuzz
     runs-on: ubuntu-latest
     steps:

.github/workflows/rust.yml

@@ -64,6 +64,7 @@ jobs:
 
   Cross:
     name: Cross testing
+    if: ${{ !github.event.act }}
     runs-on: ubuntu-latest
     steps:
       - name: Checkout Crate
@@ -101,7 +102,7 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v2
       - name: Set up QEMU
-        run: sudo apt update && sudo apt install qemu-system-arm gcc-arm-none-eabi
+        run: sudo apt update && sudo apt install -y qemu-system-arm gcc-arm-none-eabi
       - name: Checkout Toolchain
         uses: actions-rs/toolchain@v1
         with:

README.md

@@ -114,6 +114,15 @@ Please try to address them, otherwise your PR might get closed without merging
 after a longer time of inactivity. If your PR isn't ready for review yet please
 mark it by prefixing the title with `WIP: `.
 
+### CI Pipeline
+
+The CI pipeline requires approval before being run on each MR.
+
+In order to speed up the review process the CI pipeline can be run locally using
+[act](https://github.com/nektos/act). The `fuzz` and `Cross` jobs will be
+skipped when using `act` due to caching being unsupported at this time. We do
+not *actively* support `act` but will merge PRs fixing `act` issues.
+
 ## Policy on Altcoins/Altchains
 
 Patches which add support for non-Bitcoin cryptocurrencies by adding constants

contrib/act/event.json

@@ -0,0 +1,3 @@
+{
+    "act": true
+}