Add ccache support

CMakeLists.txt

@@ -26,11 +26,13 @@ set(CMAKE_INCLUDE_CURRENT_DIR ON)
 set(CMAKE_AUTOMOC ON)
 
 # Ccache support
-FIND_PROGRAM(CCACHE_FOUND ccache)
-SET(CCACHE_SUPPORT OFF CACHE BOOL "Enable ccache support")
-IF ((CCACHE_FOUND OR ANDROID) AND CCACHE_SUPPORT MATCHES ON)
-    SET_PROPERTY(GLOBAL PROPERTY RULE_LAUNCH_COMPILE ccache)
-    SET_PROPERTY(GLOBAL PROPERTY RULE_LAUNCH_LINK ccache)
+IF (ANDROID OR UNIX OR APPLE)
+    FIND_PROGRAM(CCACHE_FOUND ccache)
+    SET(CCACHE_SUPPORT OFF CACHE BOOL "Enable ccache support")
+    IF ((CCACHE_FOUND OR ANDROID) AND CCACHE_SUPPORT MATCHES ON)
+        SET_PROPERTY(GLOBAL PROPERTY RULE_LAUNCH_COMPILE ccache)
+        SET_PROPERTY(GLOBAL PROPERTY RULE_LAUNCH_LINK ccache)
+    ENDIF ()
 ENDIF ()
 
 if(CMAKE_SYSTEM_NAME STREQUAL Android)

README.android

@@ -7,7 +7,7 @@ Prerequisites:
   (https://bugreports.qt.io/browse/QTBUG-54666) what can be fixed by only patching one cmake config file.
   The build files will comment the problematic line.
 - Get KStars source code from from Github or KDE
-- sudo apt-get install dos2unix
+- Some tools are needed for the compilation: sudo apt-get install dos2unix ccache
 
 Set the following environmental variables before building: