fix github actions build

The build failed due to a conflict with ccache and cmake,
which arose due to a recent version upgrade of cmake in the
Github Ubuntu image.

As ccache didn't give us any value on a cold cache, and
little value on a hot cache (all buildroot packages are
already built and we only need to compile changed packages)
I see little value in maintaining it.

Additionally this change bumps the Buildroot version to the
latest stable version and uses ubuntu-20.04 which will
become ubuntu-latest anyway soon.

.github/workflows/release.yml

@@ -18,9 +18,9 @@ defaults:
 
 jobs:
   build:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     env:
-      BUILDROOT_VERSION: '2020.08.2'
+      BUILDROOT_VERSION: '2020.11'
       BUILDROOT_DIR: 'buildroot'
       # Stupid hack to invalidate cache from UI
       # https://github.com/actions/cache/issues/2#issuecomment-673493515
@@ -85,7 +85,7 @@ jobs:
 
   release:
     if: startsWith(github.ref, 'refs/tags/v')
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     needs: build
 
     steps:

README.md

@@ -132,8 +132,8 @@ Building
 --
 Clone or download this repository. Then inside it:
 
-- Download the latest Buildroot stable, e.g. `buildroot-2020.8`, and extract it
-- Rename it to `buildroot` (optional)
+- Download the latest Buildroot stable from https://buildroot.org/download.html
+- Extract it and rename it to `buildroot`
 - Run build command:
   - `./build-showmewebcam.sh raspberrypi0w` to build Raspberry Pi Zero W (with Wi-Fi) image.
   - `./build-showmewebcam.sh raspberrypi0` to build Raspberry Pi Zero (without Wi-Fi) image.

configs/config

@@ -1,7 +1,5 @@
 BR2_arm=y
 BR2_arm1176jzf_s=y
-BR2_CCACHE=y
-BR2_CCACHE_DIR="$(BASE_DIR)/.ccache"
 BR2_TOOLCHAIN_BUILDROOT_GLIBC=y
 BR2_KERNEL_HEADERS_5_4=y
 BR2_TOOLCHAIN_BUILDROOT_CXX=y