Merge "Disable goma/ccache with USE_XXX=false"

core/ccache.mk

@@ -14,7 +14,7 @@
 # limitations under the License.
 #
 
-ifneq ($(USE_CCACHE),)
+ifneq ($(filter-out false,$(USE_CCACHE)),)
   # The default check uses size and modification time, causing false misses
   # since the mtime depends when the repo was checked out
   export CCACHE_COMPILERCHECK := content

core/goma.mk

@@ -15,7 +15,7 @@
 #
 
 # Notice: this works only with Google's Goma build infrastructure.
-ifneq ($(USE_GOMA),)
+ifneq ($(filter-out false,$(USE_GOMA)),)
   # Check if USE_NINJA is not false because GNU make won't work well
   # with goma. Note this file is evaluated twice, once by GNU make and
   # once by kati with USE_NINJA=false. We do this check in the former