Add a _noccache option to enforce turning off ccache.

In addition, disable `CONFIG_GCC_PLUGINS` when ccache is used as it's disruptive, and tweak ccache sloppiness with safe values.
Those changes combined are giving us near 100% cache hit rate on hot cache.

linux54-tkg/PKGBUILD

@@ -262,6 +262,9 @@ prepare() {
   sed -i -e 's/CONFIG_LZ4_COMPRESS=m/CONFIG_LZ4_COMPRESS=y/' ./.config
   sed -i -e 's/CONFIG_LZ4HC_COMPRESS=m/CONFIG_LZ4HC_COMPRESS=y/' ./.config
   sed -i -e 's/CONFIG_RCU_BOOST_DELAY=500/CONFIG_RCU_BOOST_DELAY=0/' ./.config
+  if [ "$_noccache" != "true" ] && pacman -Qq ccache &> /dev/null; then
+    sed -i -e 's/CONFIG_GCC_PLUGINS=y/# CONFIG_GCC_PLUGINS is not set/' ./.config
+  fi
 
   # Inject cpuopts options
   echo "# CONFIG_MK8SSE3 is not set" >> ./.config
@@ -844,8 +847,10 @@ build() {
   fi
 
   # ccache
-  if pacman -Qq ccache &> /dev/null; then
+  if [ "$_noccache" != "true" ] && pacman -Qq ccache &> /dev/null; then
     export PATH="/usr/lib/ccache/bin/:$PATH"
+    export CCACHE_SLOPPINESS="file_macro,locale,time_macros"
+    export CCACHE_NOHASHDIR="true"
     msg2 'ccache was found and will be used'
   fi
 

linux54-tkg/customization.cfg

@@ -23,6 +23,9 @@ _OPTIPROFILE=""
 # Set to true to bypass makepkg.conf and use all available threads for compilation. False will respect your makepkg.conf options.
 _force_all_threads="false"
 
+# Set to true to prevent ccache from being used and set CONFIG_GCC_PLUGINS=y (which needs to be disabled for ccache to work properly)
+_noccache="false"
+
 # Set to true to use modprobed db to clean config from unneeded modules. Speeds up compilation considerably. Requires root - https://wiki.archlinux.org/index.php/Modprobed-db
 # !!!! Make sure to have a well populated db !!!! - Leave empty to be asked about it at build time
 _modprobeddb="false"