abuild: various USE_CCACHE fixes

- set PATH in the rootbld environment so ccache is actually used.

- drop the check for command -v ccache. ccache will be pulled in as
  build dependency so we don't need to die if its missing.

- create ~/.ccache if missing rather than die. This directory will
  normally be created by ccache itself, but we need to create it so we
  can bind mount it incase of rootbld.

- don't die if ccache.conf is missing. ccache will create it.

abuild.in

@@ -2196,7 +2196,7 @@ rootbld() {
 		--bind "$REPODEST" "$REPODEST" \
 		--hostname "build-$buildhost-$CARCH" \
 		--chdir "$startdir" \
-		--setenv PATH /bin:/usr/bin:/sbin:/usr/sbin \
+		--setenv PATH ${USE_CCACHE:+/usr/lib/ccache/bin:}/bin:/usr/bin:/sbin:/usr/sbin \
 		/usr/bin/abuild $force rootbld_actions
 	update_abuildrepo_index
 	cleanup $CLEANUP
@@ -2501,18 +2501,7 @@ fi
 
 # check for ccache presence and maybe export its path
 if [ -n "$USE_CCACHE" ]; then
-	if ! command -v ccache >/dev/null; then
-		die "Ccache is enabled; however, the binary can not be found."
-	fi
-
-	if [ ! -d "$HOME/.ccache" ]; then
-		die "Ccache is enabled; however, the user cache directory is not found."
-	fi
-
-	if [ ! -f "$HOME/.ccache/ccache.conf" ]; then
-		die "Ccache is enabled; however, the ccache configuration file is not found."
-	fi
-
+	mkdir -p "$HOME/.ccache"
 	# prepend ccache path
 	export PATH="/usr/lib/ccache/bin:$PATH"
 fi