Disable ccache.

Index: mono/btls/CMakeLists.txt
--- mono/btls/CMakeLists.txt.orig
+++ mono/btls/CMakeLists.txt
@@ -1,14 +1,9 @@
-cmake_minimum_required (VERSION 2.8.10...4.0)
+cmake_minimum_required(VERSION 2.8.12...3.20)
 
 project (mono-btls)
 
 enable_language(C)
 enable_language(CXX)
-
-find_program(CCACHE_PROGRAM ccache)
-if(CCACHE_PROGRAM)
-    set_property(GLOBAL PROPERTY RULE_LAUNCH_COMPILE "${CCACHE_PROGRAM}")
-endif()
 
 if (MSVC OR CYGWIN)
 	set(BTLS_HOST_WIN32 1)
