build: Enable custom ccache cache dir for Android

During lunch, check environment variables for ANDROID_CCACHE_DIR.
If it is specified, CCACHE_DIR is set to match. Prevents issues
with multiple versions of ccache writing to the same cache dir.

ANDROID_CCACHE_SIZE should also be specified, allowing for a distinct
cache directory size from the default. Syntax for ANDROID_CCACHE_SIZE
is the same as applied in the command: 'ccache -M$ANDROID_CCACHE_SIZE'

Change-Id: I17497a6f56347850e0fa7b8ebd4de0b5a0b13e55

core/combo/select.mk

@@ -104,7 +104,13 @@ ifneq ($(USE_CCACHE),)
     ifndef CXX_WRAPPER
       CXX_WRAPPER := $(ccache)
     endif
+    ifeq ($(ANDROID_CCACHE_DIR), $(CCACHE_DIR))
+      ifneq ($(ANDROID_CCACHE_SIZE),)
+        ACCSIZE_RESULT := $(shell $(ccache) -M$(ANDROID_CCACHE_SIZE))
+      endif
+    endif
     ccache =
+    ACCSIZE_RESULT =
   endif
 endif
 

envsetup.sh

@@ -228,6 +228,10 @@ function setpaths()
     unset ANDROID_HOST_OUT
     export ANDROID_HOST_OUT=$(get_abs_build_var HOST_OUT)
 
+    if [ -n "$ANDROID_CCACHE_DIR" ]; then
+        export CCACHE_DIR=$ANDROID_CCACHE_DIR
+    fi
+
     # needed for building linux on MacOS
     # TODO: fix the path
     #export HOST_EXTRACFLAGS="-I "$T/system/kernel_headers/host_include