[openwrt/openwrt] CI: build: fix ccache cache usage

[LEDE Commits]

ansuel pushed a commit to openwrt/openwrt.git, branch openwrt-23.05:
https://git.openwrt.org/51adcb7cd223f56984abdc27b929d16bde4284cf

commit 51adcb7cd223f56984abdc27b929d16bde4284cf
Author: Christian Marangi <ansuelsmth at gmail.com>
AuthorDate: Sun May 28 03:15:50 2023 +0200

    CI: build: fix ccache cache usage
    
    CCache cache is currently broken due to a funny bug in ccache compiler
    type detection. It seems ccache compiler type detection is very fragile
    and with the use of external toolchain doesn't correctly detect the
    type.
    The type detected is set to other instead of gcc resulting in ccache
    complaining for unsupported compiler options.
    
    To handle this problem, force the compiler type to gcc to make ccache
    correctly work and speedup compilation.
    
    Signed-off-by: Christian Marangi <ansuelsmth at gmail.com>
    (cherry picked from commit ae7b05328cf471780de8559fba845c4b564e059e)
---
 .github/workflows/build.yml | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 0fbeb5b0f5..0c0c05f402 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -302,11 +302,22 @@ jobs:
           echo CONFIG_TARGET_PER_DEVICE_ROOTFS=y >> .config
           echo CONFIG_TARGET_ALL_PROFILES=y >> .config
 
-      - name: Configure ccache
+        # ccache for some reason have problem detecting compiler type
+        # with external toolchain. This cause the complete malfunction
+        # of ccache with the result of tons of unsupported compiler
+        # option error.
+        # To fix this force compiler type to gcc.
+      - name: Configure ccache and apply fixes
         if: inputs.use_ccache_cache == true
         shell: su buildbot -c "sh -e {0}"
         working-directory: openwrt
+        env:
+          SYSTEM_CCACHE_CONF: staging_dir/host/etc/ccache.conf
         run: |
+          touch $SYSTEM_CCACHE_CONF
+
+          echo compiler_type=gcc >> $SYSTEM_CCACHE_CONF
+
           echo CONFIG_CCACHE=y >> .config
 
       - name: Configure external toolchain in container