normalize values of SYSTEM_CAIRO

Change-Id: I7ba86a2606d585b7b4351bc1fcd6d8ceebca5fd7

RepositoryExternal.mk

@@ -1073,7 +1073,7 @@ endif # ANDROID
 endif # SYSTEM_REDLAND
 
 
-ifeq ($(SYSTEM_CAIRO),YES)
+ifneq ($(SYSTEM_CAIRO),)
 
 define gb_LinkTarget__use_cairo
 $(call gb_LinkTarget_set_include,$(1),\
@@ -1085,7 +1085,7 @@ $(call gb_LinkTarget_add_libs,$(1),$(CAIRO_LIBS))
 
 endef
 
-else ifeq ($(SYSTEM_CAIRO),NO)
+else # !SYSTEM_CAIRO
 
 define gb_LinkTarget__use_cairo
 $(call gb_LinkTarget_use_package,$(1),cairo)

configure.ac

@@ -11809,7 +11809,7 @@ if test "$test_cairo" = "yes"; then
 
     : ${with_system_cairo:=$with_system_libs}
     if test "$with_system_cairo" = "yes"; then
-        SYSTEM_CAIRO=YES
+        SYSTEM_CAIRO=TRUE
         AC_MSG_RESULT([yes])
 
         PKG_CHECK_MODULES( CAIRO, cairo >= 1.0.2 )
@@ -11833,7 +11833,7 @@ if test "$test_cairo" = "yes"; then
         libo_MINGW_TRY_DLL([libpixman])
         libo_MINGW_TRY_DLL([libpng15])
     else
-        SYSTEM_CAIRO=NO
+        SYSTEM_CAIRO=
         AC_MSG_RESULT([no])
 
         BUILD_TYPE="$BUILD_TYPE CAIRO"

extensions/StaticLibrary_plugcon.mk

@@ -53,7 +53,7 @@ $(eval $(call gb_StaticLibrary_use_external,plugcon,gtk))
 # pick up our cairo libs before they're fully ready, causing problems
 # (e.g. using our libpixman and system libcairo). Depend on cairo
 # to delay build until cairo is done.
-ifeq ($(SYSTEM_CAIRO),NO)
+ifeq ($(SYSTEM_CAIRO),)
 $(eval $(call gb_StaticLibrary_use_external,plugcon,cairo))
 endif
 endif # ENABLE_GTK=TRUE