ENABLE_OPENCL should be TRUE or empty

Should make the Android tinderboxes happy.

Change-Id: Idf33106514a1d0e34566d76d97d689e7543eda3c

configure.ac

@@ -10330,7 +10330,6 @@ if test $_os != iOS -a $_os != Android -a "x$enable_opencl" != "xno"; then
 else
     AC_MSG_RESULT([no])
     enable_opencl=no
-    ENABLE_OPENCL=FALSE
 fi
 
 AC_SUBST(ENABLE_OPENCL)

sc/Module_sc.mk

@@ -19,7 +19,7 @@ $(eval $(call gb_Module_add_targets,sc,\
 	UIConfig_scalc \
 ))
 
-ifeq ($(ENABLE_OPENCL),TRUE)
+ifneq (,$(ENABLE_OPENCL))
 $(eval $(call gb_Module_add_targets,sc,\
 	Library_scopencl \
 ))